Thats a bunch of crap. The husband was justified in his behaviour. Maybe the Op didnt deserve it, but what do you expect? You think the guy should buy him lunch, for exposing his wife for the hor she is?
Actually, it sounds like the guy went easy on him. A well built guy using knuckles on a 145 lb. guy who was fvcking his wife, and he gets away with only 7 stitches? Think about that for a minute. First of all, he shouldn't have been conscious after the first blow, let alone a whole rage beating. And he was in good enough shape to drive afterwards. The last time I got beat up, I couldnt open my eyes for two days, and that was a bar scrap, with no weapons. I almost want to call bullshyt for that reason, but I'll give the benefit of the doubt.
He's lucky he has any teeth left, and his jaw isnt wired up.
I've seen what knuckles do to people. Its not pretty. You could kill someone easily. I have a pair, but I would only use them in a life or death situation.
I saw a average size guy hospitalize a fvcking NAVY SEAL with knuckles. The guy didnt have a chance. he was down for the count after three punches.
To be honest, I'd probably do the same thing, just out of pure rage. I'd like to think I wouldnt, and I wouldnt plan on it, but coming home to someone banging your wife is enough to make a lot of people snap. And if the dude came back to my house to 'mob' me, he'd be greeted by my .45.
OP, Im not in any way insinuating that you're at fault here, Im just saying a man is justified in freaking out if he comes home to that.
Be thankful it wasn't worse, and consider it a valuable lesson. You might even want to call the guy, and explain the situation you were in, and say that while you cant blame him, you didnt deserve it, and he needs to take care of the medical bills plus P+S, or you will have to sue both of them.