Feeling insane rushes of energy and pressure in the chest and neck during meditation

While not a question specifically about Buddhist doctrine, this is related to meditation, and your choice of support for your meditation, the beating heart in your case, is irrelevant, so it’s a valid question.

The simple answer is, where your attention goes, so goes your chi/prana/energy. You are focused on your heart, so you feel a buildup of energy there. But there is a “because” in your story, so thank you for providing some your background. The ‘pressure’ buildup is being caused by a block, or blockages, perhaps related to your prior engagement with Sufism. There are practices and techniques to free up those blockages found in both Tibetan and Chinese traditional medicine. Chi Gong for example, or Nei Gong in Chinese traditions. I can’t recommend anyone to you, but if you do some searching around the internet, I’m sure you can find someone near you that practices some form of Chinese medicine, and they might be able to point you in the right direction. With a bit of extra work you’ll be able to clear up those blockages and continue making progress. Good luck!

There are endless spiritual-type experiences that can occur on the road. I know people who have had similar experiences who then attach stories to it and become someone like the 'energy fairy' while bathing themselves in various types of crystals, floral scents and assault their ears with whale noises reaching decibels that would warp a clay Buddha figurine. Hence, if you allow them to solidify by attaching meaning to their occurrence, it will corrupt further investigation. The sensation of energy moving through the body is quite a common event, it's so common that most learned practitioners phase it out.

Buddhism is not generally interested in astral projection, although one can acquire and utilize various siddhis, they are not seen as the fundamental focus of the path. They're things found along the path rather than being the path.

To put it succinctly, Buddhism is the study of the Four Noble Truths and realizing them directly in the here and now.

1. This is suffering

2. This is the origin of suffering

3. This is the cessation of suffering

4. This is the way leading to the cessation of suffering

It’s just energy. The more you do it, the more it will make sense to you. I believe we observe it to learn from it. Take away any assumptions you have, and release and ask why, or just ride it out. If you’re on your back at the end of an intense meditation and you’ve brought the blood to your pineal gland, you may pump at your heart space, your shoulders will come off the ground and your extremities may do some crazy stuff. Basicallly you feel like you were plugged into an electrical socket. Nothing wrong, just big download of energy. You probably freed your pineal gland and it’s reattaching to source. That can be powerful.

It's normal to have energetic blockages in any meditative tradition, with mild ot more extreme symptoms as yours. If you meditate correctly they'll gradually work themselves out over time. Some cases it's a great help to have expert teachers to advise, but for the most part, they'll take care of themselves.

Meditations where you focus on a particular point in the body, will tend to exacerbate and focus energy into that area. And most people, when they do that, increase tension in the body instead of decreasing it. It is not an easy skill to relax areas that are tight and uncomfortable, the best most people can do is try not to add more tension. Having whole body awareness tends to help, instead of focusing on a point in the body such as the nostrils or head. If you focus more on your belly area for example, that will alleviate the head tension you're feeling.

I discuss the more general problem of energy blockages here in great detail under the section jhāna constipation: https://lucid24.org/sted/7sb/5passaddhi/index.html

That sounds like the effect of at least one of the Five Hindrances. Observing where this stagnation is physically or metaphysically and what comes to mind in practice may lead to an enlightenment on an attachment restricting your capacity to continue any further.

A small conditioned limitation, like a fear of spoons can impose on an individuals life considerably. Any of the hindrances may have a similar bottleneck effect.

Attempting to "push through it" can be done, although that would be not unlike taking a hammer to a fine tuned machine; understanding limits is very admirable in circumstances such as what you have described.

While temporary limitation was wise, it doesn't mean to shy away from the practice altogether. Acting within compassionate reason, using unbiased insight for obstacles and striving for perfection are ideals worth keeping in mind.

Cultivate in harmony

There are no "good" answers to questions like this just as there would be no "good" answers were to someone ask about why the microwave sometimes heats your dish instead of your food. It just happens. You're better off just resetting the timer and trying again. Eventually your meditation will cook properly. If you attach to experiences like this, you are in essence eating cold food.

You can try focusing on the arising, persistence and the cessation of thoughts, feelings, sensations & perceptions in general and when you get these weird states in particular.

There is the case where a monk, when feeling a painful feeling, discerns, 'I am feeling a painful feeling.' When feeling a pleasant feeling, he discerns, 'I am feeling a pleasant feeling.' When feeling a neither-painful-nor-pleasant feeling, he discerns, 'I am feeling a neither-painful-nor-pleasant feeling.'"When feeling a painful feeling of the flesh, he discerns, 'I am feeling a painful feeling of the flesh.' When feeling a painful feeling not of the flesh, he discerns, 'I am feeling a painful feeling not of the flesh.' When feeling a pleasant feeling of the flesh, he discerns, 'I am feeling a pleasant feeling of the flesh.' When feeling a pleasant feeling not of the flesh, he discerns, 'I am feeling a pleasant feeling not of the flesh.' When feeling a neither-painful-nor-pleasant feeling of the flesh, he discerns, 'I am feeling a neither-painful-nor-pleasant feeling of the flesh.' When feeling a neither-painful-nor-pleasant feeling not of the flesh, he discerns, 'I am feeling a neither-painful-nor-pleasant feeling not of the flesh.'[...] Or he remains focused on the phenomenon of origination with regard to feelings, on the phenomenon of passing away with regard to feelings, or on the phenomenon of origination & passing away with regard to feelings. Or his mindfulness that 'There are feelings' is maintained to the extent of knowledge & remembrance. And he remains independent, unsustained by (not clinging to) anything in the world. This is how a monk remains focused on feelings in & of themselves DN22

When you have distracting thoughts you can try following these instructions. for their removal.

I would advise you to keep it simple and just focus on ie a contemplation or just the arising, persistence & cessation of sensations associated with breathing or the heartbeat.