Hmmmm… If you’re character is displaying behavior that is not socially redeeming, the best way to make him sympathetic is to show the reader why he’s behaving that way - the root causes, and then throw some conflict at him.
But remember, it all depends on the story and what you’re trying to say.
To me, this guy was born and raised dirt poor. White trash. He had nothing going for him all his life except his looks. His family was the laughingstock of his community and he grew up hating being poor more than anything else in the world so, of course, he used his only resource – his good looks - to marry a rich girl.
She knows he comes from poverty and she’s not that hot to begin with so she uses her money as a form of power over him, to control him - and belittle him when necessary of course. So he gets his revenge by having fly-by-night flings with all her friends and God knows who else. She kind of knows about his little affairs, but as long as he behaves like a good little boy and displays all the attributes of a good trophy husband, she doesn’t make too much of a fuss.
This by itself doesn’t really make him fully sympathetic yet. It merely sets up for the reader why he is that way. Now you need to add some good conflict. Pose a real dilemma.
Now what if he finds himself actually falling in love with someone! A beautiful stranger, chance met, who knows nothing about him - who can totally relate to him, who he can totally be himself with, who doesn’t care anything about his looks or his money? He never knew it could be like this! For the first time - he is actually in love! Real, true, honest to goodness love!!
Now what does he do? He has sworn to never be poor again. But he is beginning to feel like he cannot live without this woman. The money or the girl???? There are now two forces driving this man. Which will win?
Place him in a dilemma that readers can sympathize with. Who hasn’t had to make a heartbreaking decision at some point in their life? It doesn’t have to be so drastic - you can make the dilemma something else – as long as it is something the reader can easily identify with.
If you can get the reader to understand why he is that way -and then identify with him, and his problems – they will be willing to hitch along for the ride and hear his story.