Amount and frequency of feeding depends on the size/quality of the pellet and also the individual betta.
Assuming you're feeding the Aqueon betta pellets, which are on the smallish side and not the HIGHEST quality, and assuming you have a standard adult betta male about 2-3 pellets twice per day should be fine. If you have a smaller/younger/small female about 2 twice per day should do it.
You can also try different amounts for a couple of days and see how your betta eats and digests and whatnot. I wouldn't recommend more then 4 pellets per feeding however.
Fasting, IMO, is optional. After ending up with a couple of boys who just positively SHREDDED their fins if their regular feeding schedule was interrupted, I don't purposely fast and so long as I don't over feed....and even on the rare occasion when I have on bloodworm night.....I've never had any fish with any sort of problems.
I depends on the individual fish, for some it could be helpful and even necessary, but over all based on my own experience I've found it mostly optional.