I would recommend that you read a book called The Culture Clash by Jean Donaldson. For me this book was so insightful even after owning cockers for 20 years.
Jean Donaldson is a respected behaviourist, who has spent years looking at why dogs behave as they do. Dogs do not think like humans, they do not have human emotions, and whilst they can sense danger in the moment thay can?t think ahead and certainly rely on learnt behaviours.
From your post, several things stand out for me. You say he was from a large ?family? of dogs, so isolation from his new ?family? is confusing. He can?t understand that you are excluding him at certain times.
Secondly you say that he?s asleep at 8pm, but then presumably you are waking him up to have his last wee at 11pm and then when he?s then awake you isolate him and go to bed and expect him to go back to sleep. Do you play with him before you go to bed?
The other thing that strikes me is that he maybe getting too much stimulation and in the process becoming more hyper.
You say that he had a lot of training with a trainer, but don?t say what that the training was. Did they do any training on timeout and calming techniques?
He?s still very young. Yes he has a lot of energy, but he also needs lots of rest, plus he now has hormones raging through his body.
My recommendation would be before you take him to gun dog training, which may be too much stimulation for him, consult an APDT trainer/behaviourist to observe him and point you in the right direction.
I?m not a trainer, but an experienced owner, who at the moment has a challenging 12 week old puppy!
Good luck and you will come out the other end.