Legal fees I have to admit I kind of memory holed at this point. The advice I got suggested I should probably sue (the seller had been sued a couple times before but I couldn't find much in the way of results) but the need to do the work ASAP meant I might end up paying twice. I was extremely wary of lawyers and had no faith they'd do anything but screw me over more than I had been.

Total costs were probably in the range 40K range.

I can also recommend a structural residential engineer if you need a third party eye to anything a vendor may propose/get your own design. RESolutions https://www.res-dc.com/