#1
Tabbing for the first time (Descending by Saturnus) and was curious if I should be paying attention to key, scales, etc? Will it making the tabbing easier? Allow me to better understand the interplay between "music" and those ideas?

Curious if it'd be beneficial on any front or just an unnecessary time sink, especially for a first time tabber.
#3
It will, especially if you're tabbing out bands that tend to stick to diatonic ideas.

Taking notice of the notes can allow you to stumble upon a particular interval that you've always been hearing in music that you really like which you can use in your own music. It also allows you to look at different ways accidentals can be used. Not every single note has to fit within the key, and when it doesn't, you can see why it works (or why you think it doesn't).