14 year old neutered male cat, spraying for over a year. Desperate to try anything

The titles says the main point. My male cat that I have had since he was 4 months old has been spraying more and more over new locations over the past year. He has been to the vet 4 times over this past year to see if anything has changed and nothing is wrong with him and the vet has confirmed it is a behavioral issue.

There wasnt any life changes that occurred around the time, my husband and I dont have kids. We have had the same jobs for a long time, or schedules are about the same most days. He gets treats daily, high quality wet food twice a day, open feeding for dry food and almost nightly play sessions as well as a new toys with a monthly Kit Nip box.

He started spraying in our basement and it took almost a month until we finally caught him on camera spraying. He then moved onto spraying in the kitchen, on the countertops and then on the oven front. Eventually we got some motion sensor air sprayers to deter him and got 5 additional litter boxes, beyond the 2 litter boxes we already had and that helped for a week or two. Or so we thought, he just started finding new locations ALL OVER the house.

We have purchased a few more air poofers to deter him from his most common places but he always finds new ones. We have 6 Feliway diffusers in the house spread out to be withing 6-8 ft of each other. We clean the litter boxes daily, scrub the pee spots with enzyme cleaner and then an orange oil to deter him but nothing seems to work.

The vet has told me I am a good person for not getting rid of him. I love him so much but I find myself getting more and more frustrated and angry.

We contacted 2 pet psychics and havent had any luck. We are gone from home to work so we can't put him in diapers and I feel so guilty to lock him in a bathroom or single room while we are gone.

His sister who has been with his whole life has not changed her behavior at all.

If anyone has any ideas I am willing to try anything, its been over a year and I find myself in constant fear of finding new pee spots. I don't invite anyone to my house out of shame and fear of the possibility of my house smelling like cat pee and/or missing a spot of pee and having them find jt. Getting rid of him isn't an option but I need to find something to help. Tonight I felt resent me towards him and its breaking my heart.

He sleeps next to my head every night and I love him so much, I just need something to change.