It is still possible to train an older cat not to bite or scratch. If he gets too excited when you are playing with him and starts using teeth or nails, stop playing with him immediately. Do not play with him until he calms down. If he bites or scratches you, make a loud cry to show that he hurt you and walk away from him. This will teach him that you do not like it when he does those things and that means less fun for him.
Do your best to ignore him if he tries to bully you for food through biting. When he realizes that the tactic no longer works, the behavior will become less frequent.
Yeah, it does depend a lot on personality, but some cats can be more territorial than others. Especially when they are looking to breed and are full of testosterone. Sexually mature cats are more likely to get into fights with other males over females.
They can also travel far away from home looking for female cats to mate with. Sometimes, they disappear for days or even weeks. The farther they go, the higher the risk of them getting lost, hit by cars, killed or injured by other animals, caught by other humans, and so on. I do not know about where you live, but I know there are places where unscrupulous people can make money off of stealing and selling another person's pet if it is a valuable or rare breed (Sphynx cats like yours certainly fall under that category). It is fine if you want to keep him unaltered so you can breed him later, but I would keep an keep on him if that is the case.
Pheromones are chemicals that every living thing produces to signal moods like excitement and fear and trigger responses to other individuals of the same species. Humans are not as aware of them as most animals. A pheromone diffuser is a spray that releases calming phermonomes to help relax aggitated/excited animals.