Specialmom has a lot of good ideas to help. And I really agree that a lot of this does sound like anxiety. 25 to 30% of kids with ADHD do have anxiety as a co-existing disorder. ( "The ADD/ ADHD Answer book," by Susan Ashley p. 53). I do think that a child of this age who has gone through what he has (not your fault), coupled with ADHD could very well have anxiety problems.
And the thing is ---- kids of this age (heck most kids) don't know how to self soothe. It is something that has to be taught. Thats why Specialmoms ideas are so good. He needs to be taught or shown how to self soothe.
And, of course, school can really add to anxiety levels. Is he on medication? And if this is a new school - thats a frightening place to a 3rd grader. Do talk to this teacher and see how he is doing. What is really important is for him to find a friend. The teacher may be able to help here. But most importantly, the teacher does need to know what is going on with him. She can make a huge difference if she chooses to do so.
Long story short - if you want him to be independent and strong, you need to teach him how to do so. Just realize it will not happen overnight.
I am also the CL on the ADHD forum here -
http://www.medhelp.org/forums/ADD---ADHD/show/175
If there is any way that I can help you with resources for that please don't hesitate to ask. Best wishes.
But the things like not going to different levels of the house or leaving the house really does sound anxiety oriented. Have you considered talking to a therapist about this?