Well if you've already made it so that the Z key is now the A button like emulators, I think it'd make more sense for space to be the run button. I personally never use the space bar to talk. Heck I didn't know that was an option even.
Poison is strong against fairy (in reality) because poison was only super effective against grass before, many grass types had dual types which even resisted it anyways making it somewhat useless.