Hello! If the Pokeballs were normal, I'd want 2 5IVs for the Mewtwonite Y, yet I would accept 1 5IV bank ball pokemon and un IV-d one. In that case, if you can only train up to 3IV (5IV would be preferable), I would accept 2 3IV ones to compensate.
As for the other 3 items you're after, 1 3IV Bank Ball and 1 un IVd Bank Ball PokÃ©mon would suffice. I'm being quite generous I think as you've always came through for me!
I think that would be fair?