Thanks for all the responses, it really does help to read everybody's stories.
So we've been trying to socialize them a bit more. Old girl is under my bed right now, with young dude sitting beside the bed staring at her. He doesn't seem to chase her under there too often, though, and she seems to be able to chase him off when he does. So at least she has a semi-safe place to hide.
Oh, now he just walked away.
No peeing anywhere other than a litter box for either of them, so that's a plus. They each have their own litter box, but each of them has used the other's. So things seem to be slowly improving. I'll see if I can get my husband to hold off on the kitten idea for now.