First, I can tell the level of concern by the length of your post. And given the fact that you are seeking professional help....it also shows how important this is to you.
Ok, lets assume, just for a second that he is just a normal very sharp kid who has gone through a bit of trauma. Intelligent kids quickly learn how to manipulate the system. And when you stepped into the game (at a pretty young age according to your profile), you and your hubby didn't have the experience to deal with this. No blame on you. I have seen lots of posts from people much older with the same problem.
When you said, "We have tried every consequence, good and bad, and he does not change." That is part of the problem. Smart kids very quickly learn that the best way to avoid consequences is to pretend they don't work. So the parents try something else and something else and something else. And the child keeps doing the same old thing. Also, and more importantly, for any consequence to work it has to be consistently and immediately repeated, and repeated, and repeated. Experts say it can take up to three weeks for the child to realize that you mean it. For example, taking away his legos is ineffective. "out of sight, out of mind". Its much better to take him away from playing with them (a timeout), and then return him to them. You can only take the legos away once. You can remove him many times.
There are some very good books that go into much more detail then what I just said. They are all very good. You can easily check out the reviews on Amazon.
the books are: "SOS Help for Parents," by Lynn Clark
One, Two, Three, Magic by Dr. Phelan
Love and logic by fay and cline
Now, I said, lets assume he is normal. If he does have medical condition, then things do change. The over all logic of the books above is still good, but they need to be tweaked according to the condition. I agree with you that Conduct Disorder is not probably his problem. I am also the CL on the adhd forum, and he certainly does show symptoms of inattentive adhd. It will be interesting to see what the psychologist has to say. But, inattentive adhd or add is often hard to diagnose. Here are two links on add that you might find interesting.
The main thing is that if the problem can be identified, then there are ways to deal with it. Hopefully, some of the info I have given you will help. Let us know what the psyc says and I can find resources to help you. Best wishes.
I agree with SandMan, but I'd also like to offer that your stepson is likely traumatized. Google "Parenting the Traumatized Child" and I think you'll find some really helpful information there. His need to always be in control of others, his quick escalations, stealing from his mother are classic symptoms. A child's first need is physical safety, and in his early childhood it doesn't sound like he spent much time feeling safe, so his brain is stuck, and is hyper vigilant just trying to make sure he's safe. When you're having him tested, look into trauma based therapy.
Wow, I am so appreciative of your coming back with an update. Advocating for our kids can be daunting but it sounds like you did a great job! Keep us updated.
What is going on now with him? Why did they finally take action to diagnose him?