When does the biting get better?

I have my fifth foster puppy, a 16 week old shephard mix former stray from northern Canada. I’ve had him for 9 weeks and he is my longest foster by far. He had parvo and was hospitalized for awhile when I First got him, and still has a sensitive gut as a result.

He Has learned several basic commands, and potty training is slowly coming along. The issue I’m having is biting. If he’s awake and I’m aeound, he bites. He’s also teething which makes it worst. I enforce naps, have tried frozen cucumbers, frozen washcloth, frozen wet food in kong and lick mat, various enrichment toys, redirecroon, reverse time outs, a shield to prevent him from biting me. Nothing seems to help. if He’s awake, he’s biting me. Nipping at the heels/toes, biting my hands, going for my thighs/upper arms.
I‘m doing all the things And no conventional methods are working. I take him for walks around my yard (he can’t go for proper walks yet as he is not fully vaccinated), work on training, and reward calm behaviour (which seems to remind him that he should bite me). I’ve come to the conclusion that he just has to grow out of it and complete his teething. When can I expect it to get better? I’ve had several foster puppies and it’s never been anywhere this bad before.