Don't know where to go from here

I have been married 2 years. I have a child from a previous marriage who is 13. My husband gets on to him for everything. He is very picky/micro mange with him. If my husband and I aruge, he will tell my son it is his fault. He even told him if I leave him, it will be his fault. I told him never to tell him, but my husbands relpy is "well, it's true". My son has gotten extremely depressed, gone to couseling now living with is father. I am broken hearted. Now my husband is starting to argue with me over anything. He just won't stop once he brings up a subject such as, not housekeeping good enough (things are clean and picked up), or how could I miss a phone call if I heard it ring when he called back. In other words, it could be anything and it usually last about 20 min. on the phone on my way to work. We work differnt shifts during the week and home on the weekends together. He wants to be with me the whole time. If I want to visit with my older children or a friend during the week, he usually thinks of an excuse that I shouldn't go and if I happen to be with them, he calles me constatnly. They are at the point to where they don't want to come around him. I am starting to get depressed and a nervous wreck.