The less you react to his monstering, the better. When he is complaining about something you are doing or have done, just say "I'm sorry you feel that way" and then walk away. The less you react to his behavior, the better. When we react to the bad behavior, it justifies to them why they feel the way they do about us at that particular time.
He is trying to find his way, but he doesn't realize that he is going about it the wrong way. He is reacting like a teenager who is flexing his muscles to see just how far he can go with you. Who knows? Maybe he's hoping that he will hit your anger mode and you'll show him the door. Whatever he does or says, do not help him out the door. If he wants to leave....he needs to do this all on his own.
You are doing great...you are not the one in crisis. Always remember, you are the prize and he needs to learn to respect you for the person that you are.
Hang in there. He is still acting out and will be for a while.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.