If he's not eating enthusiastically and his mouth and breath don't smell good, I'd get his teeth checked to make sure there are no cracked or broken teeth. One of mine in the last year had the worst breath- horrid. He turned out to have a slab fracture of one of his upper pre-molars that had probably been there for a while (that's a whole 'nother story though) and a second upper molar that was chipped but not open to the pulp. The one with the slab fracture had to be pulled and the dentist was able to bond the chipped one. That and a round of antibiotics and his breath smelled so much better. His appetite was never affected and he'd chew on bones, treats, and rawhide without apparent difficulty- the breath was the tip off. Since you haven't had Bauer since he was little, you have less of an idea what he's been chewing. If his teeth and mouth all turn out to be fine, maybe he's the unusual lab who isn't a chowhound. My dogs seem smellier on lamb based foods , or that may be my imagination.
The smell at his back end could be a number of things also. Snowshoe's boy Oban had some smell going on at the back end that wasn't anal glands, it was more on his back near the base of his tail (?) but I don't recall the problem. I'll attach an article that just goes over some of the sources of possible skin infections that can be smelly.
bacterialskin
Hope you figure it out. Let us know if you do!