As a former P45+ user, who moved to the 160 but has also shot the 180, I found the difference (besides resolution) between the 160 and 180 for my work very very nominal. The DR difference between the 160 and P45+ is a huge step at least IMO. You can also verify this with the Dxomark results. Look at the P65+ at 89 and the 180 at 91. Not that great a gap. I am sure if you look hard enough you can find it, but for me the gap in DR wasn't worth the gap in price and I knew the 180 would be very picky with the tech camera lenses. One thing I have become a believer in is Dxomark scores. Especially with DR.
I agree with Guy, if you want tech camera movements, then do consider a step down to the 160. You will easily get 10mm with your 35XL and maybe 12mm depending on the subject. With the 43XL, you can that that to 17mm and with the 60XL 30mm.
I agree the 180 is the best in possible resolution, but when there are only a couple of pieces of glass that get you there (when shooting wide) that both cost over 10K U.S., I took the lesser route.
Before you get rid of the 180, take up Guy's suggestion with a dealer and see if you can trade down to a 160. There are deals to be made right now for sure. But I can also fully understand your needs to scale back
I am feeling that too and working along the same process with 12 years of Canon lenses and bodies.
Even with the D800, I still like the look/feel of the 160/tech camera output and try to lead with it for most of my work.
Paul