Agree with the lead, I’d have a house lead on him at all times, until you can retrain the behaviour at the door simply put him away when you need to open it.
As for the firm no, I respectfully disagree, she needs to show him what good behaviour gets him and to redirect the bad behaviour to good. Have you trained him “touch”? Simply hold out a hand, palm facing him and say “touch”, as soon as he touches your hand reward with a treat. Dogs love this one and learn it really easily, it’s great for redirection, next time he’s going for your ankles simply start practicing touch and his mind will work with that instead of biting you.
Sounds like your behaviourist friend might be a great asset to you, personally I’d happily spend 70 quid to find out why my dog was doing something and what I could do to make him happier than be locked in an endless battle of wills that no one wins. You don’t need to dominate, just be calm and assertive. Good luck x