[Whit]

     On the subject of picking your battles, you've got to know how much it will bother you later. Like A seems to have been settled, I may be wrong but you seem okay with it in the long run. In cases where you'll get over it easy it's easy to walk away.
     B however... C'mon tell me your not still pissed? Are you sure of your target though? Are you pissed at the wife or your brother. I don't even like my brother but I'd go off on anybody that slammed him without just cause. My point being that she may not be worth your time, but she may not be the cause of your aggravation. Going off on her may be pointless, calling your brother a spineless prick might make you feel better. It would probably be worth it too.
     As for C, dealing with people you dislike is one of those compromises you make in relationships. This being said have you not thought of referencing one of his comments in front of your husband? If your husband asks, which he should, quote the asshole to your husband while the asshole is standing there, then offer to go get them a snack from another room. The reason I suggest this is that I've been in your husbands position, it sucks. You wind up feeling like both people have been going behind your back. Obviously your buddy is out of line, but he's easy to deal with. The worse feeling is that your SO didn't trust you enough to tell you. So yeah, stand up for yourself or he's going to feel the same way. I just suggested that method because I think it might be particularly satisfying if you pulled it off right.
     Back to my original point, don't let stuff bug you for long, if it does do something about it. Like slang bitchslapping Sycamore, it'll make you feel good about yourself. See slangs smilie? Worth a shot anyway.