Hi there. My son will be 4 in May and has many of the same issues. He was labeled as having an 'impulse control problem' in Head Start, but the psychologist we went to didn't agree. My suggestion would be to give him responsibilities, like vacuuming the playroom after he cleans it and helping you decide what to have for dinner, things that make him feel useful and keep him busy. Letting him 'help' gives him a way to be like you, which is how they learn at that age. Time out sometimes works for us and sometimes not. If my son tries to get physically out of time out, I tell him to stand right next to me with his back against the wall. He is not allowed to sit down or speak, the same rules as any other time out. This way I can keep an eye on him and usually he's distracted by what I'm doing, whether it's laundry, dishes, or anything else. The other trick is to make sure he has a nap, and eats enough. My son has to have his midday nap, or his behavior goes completely downhill. Also, try to set aside some time every day to do things with just him, like stories or cutting up paper or just Tickle Wars. Even with all this, sometimes putting my son in his room (with nothing except his bed and his dresser) and letting him have his fit is all I can do. He is not allowed to come out until he has calmed down enough to tell me why he was upset and what he would have liked to have happen before the fit started. Then we talk about it and we talk about better ways to ask for what he would like. We also talk after a regular time out.
Try to learn your son's triggers for getting easily upset, like being tired or hungry, bored or overstimulated. Sometimes even preservatives or artificial flavors or colors in food can do it.
Be sure you are modeling proper behavior, ways to deal with stress, and how to react when you don't get something you really want. They pick up a LOT more than you think. Trust me on this one - mine looks like a carbon copy of his father when he's mad. Don't let your son think that you'll do anything to keep him from screaming, that just encourages the behavior. Make sure everyone is on the same page with the house rules and the appropriate discipline, and that everything is explained to your son so he understands. We learned all of this late, and it is a major uphill battle. It's really hard to change the way your whole family acts and reacts. Talk to your doctor to rule out medical reasons, like poor hearing contributing to slow language development, so he would not be able to make himself understood. Do NOT let them tell you it's a phase or he has ADHD and needs to be put on meds. If you don't like the answer, insist on a second opinion. GOOD LUCK!!