I think you need to take a bit of responsibility for the order. Your disability is known to yourself better than any dealer however good or bad they are.
You state you have had problems with ride comfort before, so surely you would have been extra vigilant test driving suitable cars.
If you were not happy with the test drive length, you shouldn’t have ordered but researched more.
3 years is a long time if not comfy, perhaps changing cars is too easy a option instead of selecting the right car in the first place.
Having said that I hope you find a solution, good luck.