Best Pali to English translation source

I’m very new to Buddhism

Newbies to Buddhism should 1st comprehend the core message of the teachings, which is found in the 1st three sermons. If the 1st three sermons are not comprehended then the phrase of this question will be misapprehended:

‘etaṃ santaṃ etaṃ paṇītaṃ yadidaṃ sabbasaṅkhārasamatho sabbūpadhipaṭinissaggo taṇhākkhayo virāgo nirodho nibbānan’ti.

In summary, the 1st three sermons explain Nibbana is the ending of craving, attachment & egoism rather than the ending of "sankhara".

"Sankhara" is a complex term with many different meanings and is not found as an unwholesome dhamma in the 1st three sermons.

wanting to find an accurate source to show me the word-for-word interpretations of terms and words.

An "accurate" source does not exist, which is why there are numerous translations of a same sutta by different translators where each translation is different.

The above said, Sutta Central has (mostly) word-for-word Pali-English function of suttas translated by Bhikkhu Sujato, which is all of the MN, SN, AN & DN. While this Pali-English dictionary function can be used as a guide, it cannot be completely relied upon because the Pali dictionaries are often flawed.

In Sutta Central, click on the "wheel cog" at the top-right of the screen then activate the dictionary function below:

Right now I’m trying to learn the meaning of each word of the “Ethan santhan ethan paneethan..” chant and although I have the English explanation of the whole thing, I want to know what each word translates to in order to gain the best personal understanding of how this mantra is said and also how Pali works.

The verse you wish to translate is generally translated incorrectly and/or misunderstood, particularly the phrase: "sabbasaṅkhārasamatho".

‘etaṃ santaṃ etaṃ paṇītaṃ yadidaṃ sabbasaṅkhārasamatho sabbūpadhipaṭinissaggo taṇhākkhayo virāgo nirodho nibbānan’ti.

Since the suttas clearly tell us in many places Nibbana is no attachment (sabbūpadhipaṭinissaggo), no craving (taṇhākkhayo), no passion (virāgo) & no suffering (nirodho); the phrase "sabbasaṅkhārasamatho" does not mean "no sankhara" because "samatho", unlike "paṭinissaggo", "khayo", "vi" & "nirodho", does not mean the absence of something. "Samatho" means "calm", "tranquil" or "serene".

"Saṅkhāra" can be activities of body, speech & mind, which a living Buddha, dwelling in Nibbana, also has. Therefore, "sabbasaṅkhārasamatho" means the "calming of activities", i.e., a calm body, calm speech & a calm mind.

The common translation of "sabbasaṅkhārasamatho" as "stilling of all activities" gives the impression of an "absence of activities", which is wrong.

You have to memorize the whole Pali context, not only "etam santam etam panitam" part, the answer is inside the entire Sutta's skeleton already.

Start with clinging in 5 string aggregates, which is sankhara (unpeaceful; asantam)

>>

More and more peaceful by clinging in only 1st jhana-8th jhana aggregates, which has lesser sankhara, but it still has (unpeaceful; asantam).

>>

The most peaceful (peaceful; santam) is sabba-sankhara-vupasamatho.

For how is it unpeaceful, see MN Mahadukkhakkhandhasutta.

I want to know what each word translates to in order to gain the best personal understanding of how this mantra is said and also how Pali works

So other answers have already mentioned SuttaCentral.

There's also a Digital Pali Reader which I haven't tried (but which other people have, and liked).

And some of the suttas on buddha-vacana.org have "word by word" translations (i.e. if you use a mouse to hover over a word).

As for "how Pali works" I guess you need to ...

• Know vocabulary (e.g. via dictionaries, of which there are several, and/or by looking at words in context, and/or seeing how other people translate them)
• Know that words are compounded (aggregated into longer words, a bit like in German), however they're compounded in different ways (see here and/or here) -- you might need to guess at how to break a compound word into its components and look up each word separately.
• Nouns are declined and verbs are conjugated (like in Latin or Greek)

You can't afford to ignore declension. In a Pali sentence like "man dog bites" then the nouns "man" and "dog" would be declined to show which is the subject or agent in the sentence, i.e. to show whether it's saying "man bites dog" or "dog bites man" -- it's the declension not the word order that's important (and declensions might be instead of prepositions too).

• This list -- Declension of Nouns -- helps to look up the declension of nouns. See also the Pali Toolbox more generally.
• The Syntax of the Cases in the Pali Nikayas tries to explain what each declension means -- e.g. "what might it mean when a noun is in the 'ablative' case?"

Questions about Pali itself (i.e. questions about the language) aren't really on-topic on this site, though, though questions about the meaning of specific Buddhist doctrine written in Pali is on topic.

Here is a slightly modified B.Thanissaro translation of that passage (etam santam...), with pali + english lined up side by side, nearly word for word order. http://lucid24.org/an/an09/an09-0036/toc-addon/index.html

suttacentral.net is an excellent resource, if you configure the settings on there to show pali with english for B.Sujato translations (aside from KN, he has complete set of translations for nikayas). You can view them side by side or line by line.

lucid24.org has a snapshot of B.Sujato's translations as of 2019-jan., arranged in side by side pali+english, with an important correction to B. Sujato's mistranslation of the 4 jhana formula.

DPR (digital pali reader) is an offline excellent resource addon for firefox.

Those resources will save you an enormous amount of time from the tedious and frustrating old tech research methods. But with that said, don't expect to get an understanding of the Dhamma even if you read the entire Pali and English collection with a decent intellectual understanding. It's only through repeated reflection over years, and seeing how the various important terms are used in various contexts throughout the canon, and a deepening of samadhi in your meditation practice that the passages will really make sense, and you're able to sort out for yourself the various controversies and sharply divergent interpretations existing out there.