I think its a little too complex for its own good. I suggest the following:

I would reduce the potion/poison resistances to Endurance, as it's your body's ability to fight off poisons. If the potion has a spell attached to it, then it would do a Endurance check, and then if you fail, you make a resulting Will check based on the spell.

On the topic of will, it seems somewhat useless. I think Will should be the save stat for psychic magic, and will vs any influence (intimidation, persuasion, etc). This leaves Courage with only Inspiration, but its complex enough imo to still be significant.

In addition, increasing your Psyche doesn't automatically learn you languages. I think it should be your mental capacity to learn and adapt.

That's all i can think to change on a baseline level right now, and it is your system, so all of these are just suggestions.