I am sorry you are having so much trouble. It is possible that there is something causing this, but it might be a good idea to try this first:
He probably wants your attention. When he screams and cries and throws things, he gets your attention. You don't want him to get attention for negative things - only for positive things. So - and this could be hard at first, but stick with it and don't waiver - you need to react only to positive things he does. When he screams or cries, you turn to your husband and say, "I think that (his name) probably needs something, but I haven't heard him talk to me and tell me what he wants in a normal voice, so I guess I can't help him." Each time he screams and cries, continue that kind of thing. If you are alone, then wonder to yourself aloud, "I wonder if (his name) needs something, but he hasn't talked to me in a normal voice, so I can't tell." Do NOT look at him when you are saying this. If he throws something, then say, "It's too bad someone threw that, because they will have to work for money and pay to fix it. I wonder what (his name) would say about that or what he wants to talk about. I guess he'll tell me in a normal voice when he wants me to know." Even if he hits YOU, do not react to it. If he hits another person/ child, then you grab that child and comfort them and hold them (or apologize to the person and let them know that you will take care of the situation) - but do NOT look at the offender. Then, when he talks to you in a normal voice, say, "Wow! I'm so glad you decided to talk to me! What do you need?" Be positive. Don't give him what he wants, unless it is okay with your family rules, though. If he finally talks to you in a normal voice and asks for something that he can't have, then act as if you are on his side and look sorry and say, "Oh, I'm sorry, honey - it's a family rule that you can't have that. I wish you could. Is there something else we could do, instead?" Then, while he is talking to you in a normal voice, act as if you haven't seen him in a long time, and tell him you miss him and you love him (and hug/ hold him) and want to hear about his day. Reward positive behavior. He will keep up the positive behavior as long as you don't ignore him when he does it. If you are busy doing something else when he asks you something in a nice voice, then turn to him and tell him that you are busy right now, and tell him you will talk to him in 10 minutes, or so. Got it? It has worked for me 100s of times.