If any of this advice is ridiculous, irrelevant or inapplicable, then I apologise in advance.
I think that his behaviour is likely to be a mix of reactions to or reflection of his past, and reactions to his present, and normal developmental. I think that the behaviours such as stealing are a cry for help, and I agree with pp that stealing is not normal, nor is intense jealousy etc. While he is "reacting" (and communicating his needs through jealousy, stealing, manipulating) you are not seeing his unique special qualities, and not feeling positively towards him, and he is not developing and learning and loving. Obviously if you are talking in a certain tone and on his case too much as per your family's comments then he will be feeling stress in reaction to that and that will be part of the problem (no judging here, we have all been there) so that has to stop.
I think you probably agree you are in for the long haul. To cope you do need to diarise regular time for you, to do whatever you need to do to get the necessary headspace.
In relation to time spent with him, if it were me I'd zero out all my expectations and focus on his needs during those ideas, and try to be the most patient I could possibly be. I would try to deal with behaviour issues as quickly as possible, not dwell on it more than necessary, pretty much ignore it other than enforce the appropriate boundaries, and try to spend as much time as possible setting in motion helping him deal with things in a positive way, trying to put into action all the therapeutic methods, having fun, etc - even if you think you do it badly at first you will become very proficient I am sure!
He may be feeling very ambivalent - on one level very much wanting to be with you, on another missing parts of his past, feeling confused and afraid - all on top of all the things secure children of his age feel at this age and need help with.
I would probably also write down on a sheet with 3 columns my original expectations vs current realities vs what you want for the longterm future, if it were me, just so that my small brain was clear on the situation.
It is possible for children to recover from trauma and negative experiences - I am confident of this as I have seen it happen. Having said this, although I have a bit of experience I have no expertise so the above does need to be read in that context. Dan Hughes' method sounds great for all children adopted or not, so hope that helps.