I imagine the doc feels trapped now, but as Lisa said about Zak last night, you've made your bed now you have to lie in it.
I don't believe he was ever 'in love' with Belle - he was just flattered that a very young and attractive woman wanted him and took advantage, but I imagine that finding out she was a paranoid schizophrenic was a bit of a libido killer.
If the character is sticking around I don't think they'll have him dump her because that would make him even more of a scumbag, so I'd guess that once Belle is stable again she will dump him, leaving him free to prey on somebody else.