Hi J.-
The key here is consistency, which will be very difficult since you are working and attending school full-time. You need to talk to his caregiver(s) about these things, and see how they are handling it. Try to maintain consistency for a very long time- all of you do the same thing. Of course, no TV or computer time when he has been acting like that. He should be watching TV for a maximum of one and a half hours daily. You might try having him earn his TV time with good behavior. One hour of good behavior equals 10 minutes of TV or computer time. He does not get more than an hour and a half total of both. There will be a lot of tantrumming over this. Use something he can see, such as a chart with one silver star per hour. Have hime sit in a naughty chair (hold him in if you have to) for 3-5 minutes. Do not allow him to insult you as he gets out of it. Whatever you do, do it consistently. Also, ask some questions: Are other children hitting him at daycare? Is he watching violent cartoons and/or shows when he is away from you? Is he able to tell you what has happened during his day? You might try a wonderful bedtime ritual, to include a bath, with mommy attention, a story read by you, etc. Don't leave while he is still wide awake. The ritual should gradually calm him down and put him to sleep.
I will be thinking of you - S.