I don't think there is a set number of feedings he should be on. If he's empty or nearly empty, then feed him. If that means 3 times a day or 6 times a day it doesn't matter as long as he's going totally empty at least once a day. I often feed smaller meals more often than a lot of breeders. But, if your guy is able to take a lot of food and does fine with 3 meals a day and doesn't spend a lot of time empty, then I imagine thats fine. I believe that he will soon be reaching the weight loss stage. They usually hit a peak weight and then start loosing weight to get their butt off the ground for the first flight. Along with that, sometimes if your feeding enough, you'll encounter times when he refuses a meal or doesn't want as much. That is normal. However, just because he refuses a meal today, doesn't mean he won't be famished for it tomorrow. They will loose down to a certain point and then often start wanting more formula again. So again, saying 3 meals a day isn't enough information. You need to stay flexible to his needs on that day.
A word of warning though, I would not be trying to get him to roll over when he's got a full or nearly full crop. If he does it on his own, then you don't have much control over it. But you don't want him to aspirate playing rough and rolling all over the place on a full tummy. Thats just general baby raising advice for you. Sorry, I have nothing macaw specific.
Melissa