sorry but my initial reaction was >>
However i do realise this behaviour isnt on. 7 years old you say ? So i'd presume definately neuted ?
sounds behavioural more than medical but obviously you need to be certain of that first so if any tiniest bit of doubt take to the vet and make sure no urine infections/ crystals etc
Obviously yet all footwear to be kept in closed cupboard at all time, he now perhaps associates the smell with marking, could possibly the footwear be taking in smells of the outdoors/ other cats ?
Wash the footwear with simple solution, the likes of trainers and inside of nomral shoes could be cleaned and wiped out with surgical spirit.
I'd buy some feliway spray as i really do think it helps greatly with undesirable behavioural cat peeing.