Window resolution has been a pain; you're not the first to complain about the weird way it acts. We'll get it to a decent place soon, trust me.
Fusion is based on type; you'll get a semi-random result that will always share at least one of the types with at least one of the monsters you fuse to get it.
We're also trying to get the hang of movement. You can run by pressing Shift, and I think that makes diagonal movement a bit more bearable.
Leon is supposed to be a bit of a wake up call for players, but maybe I did go a bit overboard.
Thank you for your feedback in general. Useful stuff.