I'm afraid for eveyone's safety. What should I do?

I am at wits end right now. I have been trying to get help and has not been working. My 4 year old functionally non verbal child that has limited receptive and expressive speech is making family life about impossible 75 percent of the time. He throws anything and everything at the fan/light fixture, broke a window on himself with a toy, broke my toe, pinches his family members (leaving bloody spots daily), bits until people bleed, hits and kicks leaving bruises on us and him. He does these things also to himself too. He breaks at least one thing a day. He broke the printer today along with a toy car. He throws things at us and the windows. He is strong is almost impossible to restrain for long. I use positive reinforcement with him all the time. I do time outs and everything. I have even spanked him, as a last resort. Somedays I just don't know what to do, I just want to give up:( When he is sweet, he is a treasure. I love him so much but don't know how much longer I can keep him safe from himself and keep our family safe from him. I know it sounds crazy that I am actually afraid of my 4 year old but I instinctively flinch from him because of the frequency he hurts me. I'm crying as I write this not knowing what else to do.