Oh dear. That's not very fun for anybody, is it? I wish I could help--here are a couple of thoughts, but I hope somebody with better ideas will show up soon!
It may be that it's partly just a function of age (as I've mentioned before, 4 was not the easiest age for any of our three).
I wonder if it would help to disengage from the situations where you can? (Not in your second example, where things would get damaged if you didn't intervene, but in the first case, I wonder if it would be worth trying just saying, "mmmhmm" with a smile and then start talking to your husband about something interesting--and maybe his attention would be diverted from the argument he's trying to start?)
I wonder in general, too, if sometimes it might be helpful to let him see that his tone is hurtful? Let your eyes fill with tears, and tell him that it hurts you when he speaks to you so disrespectfully and treats you like you don't matter. With any luck, maybe he'd come and give you a hug at that point.
Possibly, too, some kind of "team-building" talk might be good? We had a corny family chant I dragged out periodically some years back when I felt as though I needed to reinforce the sense that our family was a team, and that we needed to work together in order for everyone to be happy--he needs to see that your family life is not a contest with winners and losers, but that you are all on the same side.
Can you get out his baby pictures once in a while and tell him stories about himself? (Maybe stories that emphasize what a sweet baby he was, and how happy he made you?) He clearly can't be really happy being so unpleasant, and maybe you both need to reconnect to a time when life was really joyous for both of you.
I hope that helps a little bit--
peace
minnie
