When the cat was checked for a UTI was he tested for other ailments. My Diabtic cat did this prior to his diagnosis. (pee inapropriately AND in his box)

Since his box WAS in the bedroom for a while, could you place it back there just to test whether he'd use it over the bed? After all, having the litter box in the bedroom MUST be better than a urine soaked bed (even to you fiance)

I know this isn't a whole lot of help. I wish you luck.