I tried using [Unit_GetUnitStat_Dodge] and unfortunately it always returned 0, it does not seem to work at all. I couldn't find any instance of it within the CoreSpells.xml as well. However putting

In the same spell works as exspected  so it seem that using TargetUnit within a GameModifier that uses <ApplyToCaster>1</ApplyToCaster> creates a bug

It is pullable however i wanted to pull it from the target im shooting at and it seem that

changes the TargetUnit tag to my shooter basically I'm pulling the shooters not the targets dodge

I went ahead and tried that second block I posted within the same spell to see if i can get the correct dodge when the ApplytoCaster is not there and indeed it did work.

The bug is that the two Tags don't work together

I agree with piffle- I think it will work without the apply to caster.

Sorry, I thought you were adding this to bows, but that wouldn't work either.

Have you tried making this into a level-up trait?

You can do BattleAutoCastSpell from a trait.

Look at the Amarian blood trait.

While I find it a bit hard to understand the logic behind what you are trying to do, this is your mod . Here is an idea on how to solve your problem, in a way:

Instead of damage bonus (or total) of (acc-dodge)*n, use acc as bonus damage and dodge as bonus armor.

This means that the higher accuracy the unit have, the harder and more frequently it will hit, and the more dodge the unit have, the more armor it will have.

The armor against the arrows can be added by 1 of two ways- adding it directly to piercing, and update the other weapons accordingly, or create another attack/defense type, though it might take some work and might be bugged.