My heart goes out to you. I had a son just like the one you are describing. I didn't know how to deal with him either but I did find a few things that helped a great deal.
Try to notice small improvements in your son's behavior as you work with him. Your son probably needs a very strong structure in his day. To him, it may be important that you eat at the same time each day, that you have the same bedtime each night, etc. The rituals involved with meals and bedtime are also very important to him... eating off of the same plate, using his special spoon, hearing a favorite bedtime story, etc. This is true of many, many young children. If you take him to the store when he should be having lunch, or a nap, he will be much more difficult to handle.
If it is absolutely necessary for you to take him out in public when he should be eating, be sure to take something with you for him to eat. A handful of crackers can make a huge difference in his behavior. If at all possible, you should try to be home for his naptime every day. For the most part, your son's needs will have to play a huge part in the planning of your days for a while.
Separation from you also appears to upset him. That is why he does not want to be left in the nursery at church. Is it possible for you to sit in the nursery with him?
As for wanting to do everything himself, as far as it is possible, you should let him. If it won't hurt anything for him to do it, you may have to practice patience while watching him struggle with learning "big kid skills". Of course, you can't let him cut up an apple for himself or things like that, but it might be ok for him to dress himself, even if his clothes are put on backwards or he has to ask for your help after struggling a while.
It takes the utmost patience to get a child like your son through these difficult months but, slowly, you will notice him having fewer and fewer outbursts. He will learn that you love him no matter how he behaves and that you are there for him no matter how he feels. I'm sure that, as things are now, he is even more miserable about things than you are.
Also, you do not have any idea of the personality traits that your son may have inherited. Unfortunately, that is one of the difficulties with adopting a child. You do not know much about the personalities of the biological contributors of your son's genes. Nor can you know what he went through in the womb. You can google "prenatal influence on the unborn child" and read all kinds of interesting information.
You have your work cut out for you but, if you focus on your love for your child you will get through this difficult time. You may find that your son needs more time and attention throughout the various stages of his life. Still, through time, as he learns that you are there for him no matter what, you will find that the rewards far outweigh the difficulty.
My youngest son, who had all these problems and more because of a brain injury, got through all of this and is now a lovely, young man and one of my closest friends as an adult.
I wish my best to all four of you.