I am so sorry you are haivng this trouble at home. To tell you the truth, if male cats have sprayed more than 1 year, the chances to stop this habit are close to zero. Since you have 2 other males, it can get worse because of their presence. However, if you are willing to try one more time, plz, keep him in a room away from the other cats and give him his own litter box, his own feeding station, use feliway plug-in in the room, discuss with your vet use of prozac(fluoxetine). You are doing this for at least 6 months. The problem started because he got neutered late and he has strong sense of his territory. If he has own secured spot, like a room he can stay alone or with people only, and reduce his anxiety about his territory with some meds, you will get the best chance to stop him from spraying.
-Galloway Cat Clinic