"How will eating a jar or two as my sunday cheat impact my progress and digestion?"
Well, you should have a strong stomach considering eating an entire jar of natural peanut butter supplies 2,940 calories!
That's really more than a cheat meal; it's more like over indulgence unless you plan on eating little else that day or you're just a really muscular and/or active person.
So how can it affect progress? Most likely negatively, unless you're one of the few who can get away with that sort of indulgence or don't mind excess weight gain.