Thank you for the compliment on Sally. Currently, both of my dogs are well past the puppy stage, although with Henry, (the Tri), one may not know that.
You have the right idea about the nipping and biting. It is very difficult to teach them to have a "soft" mouth while they are still teething. However, puppies explore their world through their mouths, so by yelping and saying no, as well as offering something they are allowed
to have is absolutely correct.
We have a thread all about "Nipping and Biting" in the Behaviour Section.
The other thing you mentoned, about the puppy becoming overly tired, is a very good observation. Like small children, it's a myth that the more excited they become, the more tired they will become. You are absolutely correct thinking that it winds them up to a point that makes it even more difficult to settle. A few minutes in the crate is an excellent idea.
Remind yourselves that all the time the puppy is teething, nipping and chewing will be an issue. The good news is that once their puppy teeth fall out, it is much easier, and far less painful to teach appropriate mouthing. Labs and Goldens often show their affection (when they are older) by putting their mouth on your hand, in my experience and opinion. In the meantime, redirect as you are doing.
Lastly, most puppies start to have what we call the "Zoomies" usually around bedtime, or in the evening. With children, I call it the "witching hour" even though it often lasts longer than an hour.
With time, it will probably become one of the highlights of your day watching your baby zoom all over the house. Puppies do very well with routine and consistency and that includes bedtime.
You are doing very, very well with such a young puppy. I am sure you will see lots of improvement over the next four weeks, and even more than that over the next eight. Enjoy every minute with Jax.
By the way, Sally lived to be 13 and I never remember her being "old". ♥