I am not sure why you attract these folk with problems.. Where do you meet them as a norm? I wonder if it's worth trying something new. And I wonder too if that it's your own kindness and understanding (you seem to come over as very patient with this 48 year old man, wanting to over-look the bad behaviour even tho he's given you the ring-around) that makes them want to be with you? Some people like to abuse kindness. Perhaps being a little more strict with yourself and how much rubbish you put up with may help - it certainly will help with the heartache anyway. You really do deserve better, and to be with someone who's as kind as you.
How is your own self-esteem too? Sometimes feeling unworthy can attract the wrong sort, whereas giving off a vibe of confidence and self-worth can attract similar sorts.

Anyway, please ignore me if am talking rubbish! I wish you well, and please be kind to yourself while you heal. Go spoil yourself, do something nice, see a good friend.

Hugs.