Danner are US made and hold up awesome. I have 3 pairs of boots and shoes and never had any issues. They also look great.

I have an old house with uneven floors due to sagging joists and have talked through a few options, but eventually just put on flooring that made the uneven spots less obvious. Getting shims in all the right places and at the right heights is gonna be really difficult if not impossible. It could end up worse or more likely just squishy feeling which will cause problems with whatever flooring you use. If a structural engineer said nothing is dangerous that's good. Leveling compound is an option, but can also be tricky to do right and make sure you understand how much it weighs before you pour it and some versions are made to weigh less. I kinda came to the conclusion that the only way I would want to fix this is pulling everything out and sistering the joists which ultimately wasn't worth it for me, but it sounds like you're down for a lot of work so I would just go all the way. I also did one very small section only on my house (a bathroom) with leveling compound and it turned out good. That was a cracking tile floor though that needed to get redone and I wanted a nice level base for that and the tile can get laid right onto the leveling compound so it made sense. If you do go with leveling compound, seal everything up and add the maximum water recommended to thin it out and mix it with a strong drill with a handle on the side to be confident there's no clumps in it and it'll spread smoothly and even then you'll need a rake or squeegee to spread it out. I also put metal mesh stapled into the subfloor before pouring out to really reinforce it Incase there's anymore movement to prevent the tile from cracking.

It is really frustrating that there's no info on this after you get the test. My house tested .9 PPB and I got a Brita lead filter to be safe for making formula for our two kids. We didn't filter everything for sure and they never had lead show up in their blood tests which I think are mandatory for young kids in DC.