how do I let go of everything?

You might try looking at: The Failings of the World — Lokavipatti Sutta (AN 8:6)

It begins:

“Monks, these eight worldly conditions spin after the world, and the world spins after these eight worldly conditions. Which eight? Gain, loss, status, disgrace, censure, praise, pleasure, & pain. These are the eight worldly conditions that spin after the world, and the world spins after these eight worldly conditions.

“For an uninstructed run-of-the-mill person there arise gain, loss, status, disgrace, censure, praise, pleasure, & pain. For a well-instructed disciple of the noble ones there also arise gain, loss, status, disgrace, censure, praise, pleasure, & pain. So what difference, what distinction, what distinguishing factor is there between the well-instructed disciple of the noble ones and the uninstructed run-of-the-mill person?”

If it's any help, maybe remove not "the thing" but instead the feeling you have about the thing.

I read your saying, "How can I let go of those who [etc.] [and] those things I wanted [etc.]? Its just so tiring to hold on to all this pain."

So perhaps you want to let go of the "pain", and what occasions that pain -- which isn't necessarily "those who" and "those things" -- what occasions the pain how you feel about them, e.g. "I wanted" etc.

And maybe a way to let go of that kind of feeling is to understand that it gives rise to pain etc. -- and so, what you thought was desirable is, considering that it causes pain, not desirable -- and so maybe abandon it instead of 'relishing' it.

I think the above is more-or-less what first the three Noble truths are about.

The other thing is to replace your present motives ("I wanted") with something else -- i.e. generally "ethical" behaviour, also right view, eventually non-remorse (as a result of not doing the wrong thing) and so on.

Q: How can I let go of those who I cant remove who abuse me?

you have to forgive them first. this is according to V. Bhante Vimalaramsi that explains that forgiveness is the path to peace. He expounds TWIM (tranquil wisdom Insight Meditation). There is a book called, "GUide to forgiveness meditation"

People come to Theravada from places of great suffering. That's what drew me. It works. But it's not about shutting down and suppressing everything. It's about understanding. What is the source of your pain? How should I act differently? Ajahn Nyanamoli understands this. However, he is hardcore. You don't need that level of sense restraint at your point. Try loving-kindness. There are many ways to do loving-kindness. Try a few and see what works best.

All the Dhamma practices are to dissolve our attachment to the world.

The whole Dhamma is considered to have only one taste (rasa) i.e. the taste of Liberation (vimutti-rasa). The sole function of the each and every part of Buddhadhamma (out of 84000 dhamma-khandas) is liberation from suffering.

The path to liberation is mentioned as Noble-eightfold-path (ariya-atthangika-magga) i.e. Virtue-Concentration-Wisdom (sila-samadhi-panna).

We are required to sincerely start practicing the path with dedication.

A good start, I think, is to read the Fist sermon of the Supreme One (Dhammacakka-sutta) and it's explanation Saccavibhanga Sutta along with the Commentary (Atthakata).

Is there practice that I can do that will help me dissolve my attatchment to the world, my family, my life any hopes and dreams, its all transient and causes massive suffering for me.

The only solution is to permanently destroy the defilements (kilesas); more accurately latent-defilements (anusaya-kilesas). latent-defilements can only be destroyed by destroying ignorance (avijja). As long as we have not completely destroyed ignorance, the latent-defilements give rise to defilements again and again in the future.

Ignorance can only be destroyed by realizing the drawbacks of everything in the world without a remainder. The step by step contemplation of the drawbacks is called insight-meditation (Vipassana).

In order to start Vipassana, we are required to have a concentration (Samadhi). In order to start Samadhi, we are required to have virtue (Sila).

The whole process is considered elegantly explained in Visuddhimagga (the-path-of-purification). You'll be amazed if you read it sincerely.

How can I let go of those who I cant remove who abuse me, those who I love who are leaving me, those things I wanted to create that will never happen?

You can read the Dhammapada Piyavagga (the chapter on like/love) to find advices on this regard. Don't forget to read the commentary of it (dhammapadatthakata) for knowing the context of each verse.

Its just so tiring to hold on to all this pain.

While starting the above mentioned gradual path, you can start seeing the drawbacks of sensual world (kama) including wealth, relatives and passions that create the rough part of the suffering.

Reading Mahadukkhakkhanda-sutta and Kama-sutta is, I think, a good option for this.

It's a terrible quagmire, isn't it? How can the fettered become unfettered? The marvellous thing about being fettered is that when one investigates how they are fettered, one only finds the inside of a toilet roll tube. In the traditional literature, (Phena Sutta) the Buddha referred to volitions being like banana tree: hollow and empty, but I used a toilet roll tube, not least because it has some interesting connotations regarding attachment to form being pretty shit, but to understand that, one needs to do some wiping, perhaps making quite a mess along the way. When you get to the end of the toilet roll, you're left with a hollow shell which is synonymous with emptiness.

You might visualise the Enso paint stroke in a similar fashion. It starts out thick, and as the circle is formed, it tapers off into nothing. The circle never actually completes itself: one just disappears.

Although nobody is actually fettered, we have to approach the whole nonsense as if we were, so that, ironically, we can see that we're not.

To be able to let go of what can't be made one's own, isn't under one's control, no refuge, a pain, requires gratitude. If there isn't gratitude for what had been received, given, but instead ideas of rights, claims, there is no such as letting go but just aversion and dislike, based on still wishing to gain control. Goodwill and gratitude allows one to move on for higher, move on toward the unbound, deathless domain, following the Arahats, their path.

The pain you speak of is telling you something is wrong, it is the best teacher you have. You acknowledged that you need to let go of something ie attachment to "The world", so you know basically what needs to be uprooted, so your actually doing awesome so far. Now, how to shake those deep roots out. If you make a list of the things in your life that are causing pain and then write beside each one what you were expecting from it. Then review them again and ask what is the reality of those expectations. Lets say you have a sick child and your expectation was that they would grow healthy and go on to do things that "normal" people do. Now what is the reality? There is no such promise made, no one gets out of this life alive and everyone you know will pass. Do this with your list and then remember that everything in the conditioned world will change and that peace of mind can only come from the silent unchanging part of the Universe. Let that be your anchor, your island anytime you feel pain arise. Never give in to masochism, it is a dark path. Recognize when it arises and abandon it completely.

How can I let go of those who I cant remove who abuse me,

Ouch. This question goes deep. There is much pain here.

Regarding abuse, there is one sutta that stands out. AN6.54 speaks about those who abuse and their impact on the world. If we have to face unremitting abuse, we can perhaps face the pain to understand its source. Understanding its source, we can mitigate its impact, perhaps gentling it somewhat towards harmony.

Here is the story of a monk who abused others:

AN6.54:1.3: There he abused visiting mendicants; he insulted, harmed, attacked, and harassed them.

This is a long sutta, too long to post here. But perhaps this sutta may help you find your own answers on how to deal with those who abuse and cannot be escaped.

And yet, having understood those who abuse, there is still abuse. In this case, perhaps the story of Venerable Puṇṇa may provide some encouragement. Venerable Puṇṇa voluntarily went to a rough place where he was likely to be abused.

SN35.88:5.3: If they abuse and insult you, what will you think of them?”
SN35.88:6.1: “If they abuse and insult me, I will think:
SN35.88:6.2: ‘These people of Sunāparanta are gracious, truly gracious, since they don’t hit me with their fists.’
SN35.88:6.3: That’s what I’ll think, Blessed One.
SN35.88:6.4: That’s what I’ll think, Holy One.”
SN35.88:7.1: “But if they do hit you with their fists, what will you think of them then?”

May you find a sure path to end suffering and may peace and happiness gladden your heart.

That practice (development) is called the Noble Eight Fold Path. It starts with Right View. To develop Right View you must start to gain knowledge about the Four Noble Truths. It is only by developing Wisdom that you can truly let go.

You came into this world thinking there is pleasure. But that's not the case, is it? So, start there. Here and now with what you have. Understand the suffering nature of this existence - with birth, ageing, sickness and death, whether it is in the human world or in a divine realm - existence is suffering. i.e. if you think if I can exist apart from these problems I face today, that Wrong View is still included in the suffering. Then, find out how did I get into this mess - what is the origin of this suffering. Then find out the cessation of that very same suffering and the path leading to that cessation.

Try this video and do the meditation explained at the end of it. Use the practical examples you face today that will help you really understand the Tathagata Dhamma and find the solution you are looking for.