Have you tried validating his angry/upset/feelings? When he is mad, etc, get down on his level and say something like, boy you sure are mad. Sometimes all kids need is for someone to understand they are upset.
Given all that has happened in his world in such a short time, I don't blame him one bit for acting out. Give him some time. If he doesn't start settling into a new routine soon (it takes on average 30 days for a routine to feel normal for a kid usually, some kids take longer, some kids take shorter times), then maybe start looking for counseling for him.
Give him as much mommy time as possible. When he is so upset, ask him questions, try to get him to talk about what is bothering him exactly. Make sure you let him know you love him no matter what, but that you don't approve of his actions. Give him choices so he can feel in control of things. My 4 year old doesn't do well with transitions. He will have major meltdowns with them, just everyday things too. What helps is give him 2 choices with the same end results. For instance leaving school, he doesn't want to leave, he enjoys playing with the "new" toys and other kids. I tell him he can either put the toys away and walk out to the car, or I'll take the toys, put them away and carry him out, but either way it is time to go to the car. So far, he has chosen the first option. He puts the toys away, I get his bag, he takes him hand and we walk out the door. No fit, no fuss.
Children have the need (like all of us) to be in control of something, anything, in their daily life. Tell them what needs to happen, then give them 2 choices of how that can happen. They feel in control by getting to chose which way it will happen. You still get the desired end results that you want, but they get to choose how it happens.
Something else that might help, get him a punching bag. When he is upset and wanting to hit you, try redirecting that to something he is allowed to hit. He needs to get his frustrations out, and now is the time to teach him that there are things that are appropriate to hit and things that aren't. Hitting you will not be tolerated, however, hitting a punching bag is acceptable.