I'd like to say two things, but I am not yet an adopter so please feel free to ignore if it doesn't sound right.
The first is about the sleeping. I feel there is a lot of pressure, for adopted and non-adopted children equally, to somehow 'make' them into good sleepers. There is a sense that if your child needs your help to go to sleep, you are doing something wrong. If you give your child what they need, you are making a rod for your own back.
I feel it is worth taking a step back and asking yourself, WHY are you not content with how DC has been going to sleep until now? I know some people think we are spoiling DS, by sitting by his bed until he is asleep. They say 'but how will he ever learn'. They say 'you won't be able to keep doing this when DC2 arrives, so you'd better teach him sooner than later.' But we are happy the way things are. Bedtime is a doodle, PLUS I get some time to just chill with my phone/tablet/kindle (although to be honest it rarely takes more than 10 minutes, but sometimes I just stay put because the chapter is too interesting!).
Sometimes we suggest to DS that we could change things, and sometimes we try things differently per force (such as when on holiday) but overall we'd much rather have calm, content evenings, than regular battles over bedtime.
The other thing is about the play school. It just happens that yesterday my (birth) DS disclosed to me how he used to be terribly sad, and how he used to scream and cry, and try to run after me, when I dropped him off at nursery school. Talking about this, he had tears in his eyes.
This was exactly a year ago, when he first started there. It was difficult, he didn't like being left, and at times 'had to be peeled off me' as you put it. Every time, the staff called me about 15 minutes later saying that he was fine now. After about 3 or 4 weeks it became easier, and now he is very well settled there. The difficult start is soon forgotten, right?
Except apparently it isn't. It has stayed with my DS and at 3.5, he still remembers the distress he felt at 2.5.
Yes his behaviour changed to 'fine' soon after I had left, but wouldn't that be simply because he had learned that he couldn't change anything, that his distress was not being addressed, didn't he simply learn to bottle up his distress?
This with a BC with no apparent special needs or anything.
It left me heavy hearted I admit. Obviously it will not apply to every child in every situation, but I have promised myself that for any future child of ours, I will trust my instincts more and won't be pressured into 'having him peeled off me' or 'just go, it's the best, you're just prolonging the stress by not leaving'.