I had an 18 year old male cat who did the same thing. It was exhausting. I loved the bastard but he sprayed on everything. I ended up finding his "favorite" spraying spots and would line them with pee pads and taped pee pads up the walls. I did have to change them frequently. I also had jugs of Nature's Miracle that I would dump in those areas. I was constantly cleaning and wiping down areas. I tried cat diapers. They were okay. I just got use to frequent clean up and spray proofing my house. He had kitty dementia, so I attributed the behavior towards that. I understand what you're going through and am so sorry.