Here's what an abused man looks like, from the ones I suspect are abused. He's a typical average man, but obviously browbeaten. Much like an abused woman, he's afraid to say anything that might get him in trouble. He's quick to come to the defense of his abuser, out of fear, I suspect. He agrees with everything the abuser says and keeps quiet, his eyes downward. He's also a loner, afraid to make friends.
Writing about an abused woman is more commonplace in books, but an abused man seems just as sad. With every character, they're fighting an inner demon. So for my book, this character's inner demon is the abuser. He'd like to leave the abuser, but can't for some reason. If he's married, maybe it's because of the children or for financial reasons.
They also have an outer struggle, like with every character. It might be that he's having problems at work because of the abuse at home. It might be a fear is keeping him up at night, or even that he's thinking about fleeing one way or another.
The abused man is an interesting character. I, personally, just want to take any abused person or animal home and help them heal. That's what a writer has to do--make the reader want to help and want the abused person to succeed.
If you're abused, please get help. It can be from a professional, or even from a neighbor. I know too many people like this who are afraid to get help, out of fear. Go outside your comfort zone and seek a way out. No one should have to live like that, even a character in a book.