And I wonder if it's a territorial thing, because your boyfriend is (obviously) the male in the house, the cat is trying to establish territory for himself and feels like he has to do this?
Yeah, a trip to the vet just to make sure he's healthy...and odor neutralization, and perhaps a stress reliever like Feliway until he feels comfortable in his new home would be the way to go. I can tell you, after a few weeks in his new home, my cat's personality changed completely. You don't get to really know what kind of cat you've got until you've had 'em a little while I think.
On a similar if unrelated note, my friend Sam was posting on FB about how "gross" her cats are and how they are "jerks" because they pee on things. Come to find out she has two intact male cats. For Pete's sakes! I was like, how on earth can you judge these cats when you are in a tiny apartment with them, two intact small dogs, and three LOUD little kids, and they're not even fixed!!
She said the cheapest neuter she could find was $50/cat and she couldn't afford that. So I'm probably going to pay for them to get fixed. While I was visiting, they were fighting too and one of them has a missing patch of fur where the other tore into him. I'd take the cat that's getting beat up off her hands if she'd let me, but she says she doesn't dare get rid of him because her 5 year old son loves him and he'd be upset. Spikes is an absolute lover of a cat, he was all snugged up on my lap purring much of the time. I really think if they'd get all the animals fixed, things might be a lot better in that apartment... She's been taping ladies' "pads" on the dogs, taped around the middle, to keep them from peeing all over. Not sure if that's even OK. Doesn't seem right to me. But she doesn't want to get one of them fixed because he's supposedly pedigreed and breedable. I don't like this situation much, I gotta say...for too many reasons.