He was mouthing quite rough from 7.5 weeks tho?
at that age they were testing their teeth out and this is where the bite inhibition training started - and was basically puppy biting not mouthing per se
in their teens they do mouth and grab and all manner of antisocial things - adolescence is a trying time in any species and you have to start by going back to basics and its not about why is he still doing this, he's doing it again as he's now a teenager and pushing boundaries and unfortunately he's much bigger than he was as a tiny pup.
You do sound like you need more professional help though to point you in the right direction (and someone who uses positive/non-aversive methods).
In the meantime - short training exercises to try and focus him and getting him to bond more with you so he will eventually listen to you.
However there are no quick fixes as adolescence in itself can last till they're mature around the age of 2 years and while he may not be as bad as you think he is now he may just keep presenting with the odd thing that makes you feel as if you're going backwards again