Sorry about disappearing but I decided to quit the internet research, stop panicking and analyzing every aspect of my puppy.
I focused on getting to know him better and creating a connection while applying the methods you suggested above.
I needed to figure out how much exercise and other activity he needs, how to calm him down and he really needed to get used to touching and handling, so slooowly things got better.
He still bites, but much much less (I don't need to walk in boots at home anymore!) and the biting is mostly connected to playing and sometimes him not getting what he wants but we're working on that.
Thanks again for all the advice, it really helped.
And as you said multiple times, it takes time, patience and consistency and it will get better.
Glad to hear it. I'm happy to hear that you're working on relationship building. This makes things so much easier in general; teaching, living with, etc.