1.) I mostly only do gen and I'm not comfortable with het or slash. I know the majority of fandom aims toward slash. Is there a way to be sure I'd only have to write gen?

For the record, I have participated in the reversebang a few times now and I would probably put myself in the group which is happy with anything the other end comes up with, be it gen / het / femslash. I certainly don't fit into that majority group you speak of. ;)