Re: @Len After 50 weeks
"if Sweden wants him, they take him. At the end... they return him back to the UK"
I'm not sure about the last bit. The extradition proceedings from which he was originally bailed were to return him to Sweden to face charges. After that process ended, including any sentence which might have been imposed either Sweden would have let him go free, dealt with any extradition proceedings which might have started in the interim or deported him as appropriate. I don't see why this would have changed; the bail charges here have been dealt with so, on completion of his sentence here, then there's no reason to demand his return.
"That said... how he behaves in prison is going to determine how well he survives."
Presumably you meant in a US prison. He could, of course, misbehave in a UK prison to extend his stay as a guest of HM hoping that a subsequent US government will simply ignore him.