I haven't had much like finding a really solid source that explains how basic stats like:

DEX/STR/VIT/MND/INT/PIE affect crafting/gathering

and also stats like control/perception/magic as opposed to regular craftsmanship etc.

If someone could guide be on how this works I'd appreciate it!

Bonus Question:
What is the max amount of materia you can meld to single piece? I've seen quad meld O.O