You have to learn how to fight and disagree without putting each other down and screaming over nothing. Before you get into a fight, ask if it is even worth winning a stupid argument if you lose him. Choose your battles better.
Bring back some romance, do the things that you used to do when everything was good.
On another note, it sounds like he is pretty much out anyway by setting a deadline like that. Remember HE has to work on it too, as it wont just work out by itself. (Although don't fight about this, have a decent discussion on what each of you could do better in the relationship and agree to it).