One adult mouse is fine for a snake that size, especially a male. They only eat a few times a year in nature so you're actually spoiling him by giving him a mouse a week.

Remember, snakes are opportunistic feeders and will eat as much as they can when food is available because they don't know when their next meal will be. If you feed him as much as he can eat now, there is a good chance that he will stop eating for several months until he 'catches up'.