Is it alright to put an indoor only kitty for the past 12 years back outside to live?

My 12 year old male cat is now on kitty prozac for inappropriate urinating outside of box. (he has been to vet multiple times to check for physical problems) This behavior has been going on for 5 months (caused by male Tom cat arriving outside our house) Male Tom is now gone but my cat still pees everywhere. Vet diagnosis - its behavioral hence kitty prozac. Cat has been on meds for 2 weeks and still peeing outside of box. (have tried feliway spray, feliway diffusers, collars... citrus sprays, vinegar, bleach) you name it I have tried it. (placed him in bathroom with food, water and box for a day- bought brand new box for him) He was a stray when I found him 12 years ago and was outside cat. He has lived with me for 12 years inside. I cannot take him spraying on my sons boxsprings, curtains, guest bed, on all my clothes in my closet and my washer/dryer anymore. Is it possible for him to live outside again?