I wanted advice as to whether there was likely to be a way to pick or upgrade a seat on that leg. As Delta dont have my flight in their system in any way that I can access to upgrade seat it is left to KLM/AF sites to do it online. Uprgading an economy flight at a cost of 4000€ is crazy. At present I am going to wait until check-in and see if anything is offered. If not I will have to ask Delta at the gate I expect?

The transit is in DTW and requires that I go through US Immigration, which is why 1 hr 25 mins felt like it was cutting it fine. I've never flown through DTW. I don't have anything to base that on except that Immigration might eat up a big part of that time.