My cat is peeing on random things and I've tried everything.?

Okay so I have a fixed four-five year old cat that is still people on our clothes, rugs and carpets in the kitchen, laundry room, and half bath all next to each other. This is an ongoing problem that we've had since shortly after moving here in 2008. It started as him peeing on and around vents in the carpeted dining room, eventually peeing on every inch of carpet in there. We switched that room out to laminate floors, and upon pulling up the carpet in that room we found out that a large animal had previously used that room for a bathroom before we moved in. This kept him at bay for 3-4 weeks until we noticed him starting to pee on and around the vent in our carpeted living room nearest the dining room. Although the frequency was serverely less than before. 1-2 times every couple of weeks that we could catch and clean within hours. We changed this floor out to laminate as well and it kept him at bay for a couple of weeks. Now he's peeing in the ktichen, laundry room (where the litter boxes are) and the downstairs half bath. All tile. He's now peeing on rugs, carpets, and clothes. Basically anything left on the tile floor or on the kitchen side of the living room. We have spent hundreds of dollars on vet bills to check for problems, he recently had a UTI which we've gotten rid of but he's still peeing on stuff. We've also spent hundreds on Feliway diffusers and sprays. Which seem to work for the five feet around the area i used them on. But I'm afraid to put them into the problem areas for fear that he'll just move back to peeing in the living room. My wife thinks our four year indoor cat should become an indoor/outdoor cat which I'm completely opposed to since our neighbor lets their dog run without a leash and people drive highway speeds into their driveways. I am out of ideas.