You're not alone in questioning the sticky feeding chart on this site. I don't see a problem with lengthening the time between his meals, now that he's an adult, & if you're sure he's actually overweight. I don't think I'd jump right from intervals of 2 weeks to 3 weeks- you don't want to go too far the other way- & btw, it's very hard to get a snake to slim down once they gain too much weight, either thru reducing food or by increasing "exercise"- because their bodies are designed for fasting.
I'd probably go with feeding every 17-18 days for a while, & offer nothing when he's in shed. (-if you were feeding at that time?) Many keepers have shared that adult male BPs do best on a diet of small rats, but there's some variation in how "small rat" is defined, & I'd imagine some snakes may also have a little different metabolism than others have.
Thanks so much for the information and advice. I'll see how he responds to 17-18 days and keep an eye on his weight and behavior. I haven't been offering during shed for the simple fact that he always refuses. Might as well save him and I both the stress.