Personally, I wouldn’t start out at 5000 calories despite what Rip said. I’ve been there, done that and I got fat as hell. Yes I made strength gains, but I could’ve made those same gains and not put on so much damn fat. For reference, I’m 6 ft 3, 208 lbs and gain on around 3000 calories now. Maybe you’re taller than me or more active than me. But if you’re a typical person, you’re main activity is lifting weights 3-6 days a week and that’s pretty much it. Not that calorie demanding of a lifestyle.
I’n not sure if you realize how much 5000 calories really is. I think there are maybe 10 days in my whole life I can say I’ve knowingly had that many. Hell, if I ate Taco bell 3 times a day I would barely hit that.
Why not try increasing what you’re eating now by 500 or so calories, weight yourself and see if you gain a pound or so every week?
As for whether you should eat less on your off days, maybe something like 200-300 less if that. Usually my diet stays the same except I don’t have my pre-workout shake which comes about to around that.
But really, Rip has made people consistently stronger and knows what he’s doing. But blanket nutritional advice like that is extremely faulty if used wrong.