I scanned through a couple posts and I disagree with the one that said he should be drinking 38 oz of formula each day. Different babies have different needs. Your dr can advise you on how much your baby should actually be drinking each day. My son is almost 6 months old and he only drinks 20 oz per day. He is gaining weight just fine and developing perfectly. Formula companies will try to convince you that babies need more, but that's because you will buy more of their product that way.
As far as the spitting up, maybe the increased amount is too much for you baby. Try giving him just 5 oz at each feeding and see if the spitting up stops. If it doesn't, there are formulas for babies who spit up frequently, you could try one of those. It takes 48-72 hours to see a difference from the formula.
Does your son take a pacifier? My son cries when his bottle is empty but if we give him the pacifier for a minute it calms him right down. (it otherwise stays in his crib)
It is possible that your baby has acid reflux, but I wouldn't think its likely since this is a new development. My son has very severe acid reflux and has since he was a couple weeks old. My concern would be that many drs and parents are quick to medicate, and at times its not necessary.
Its normal for babies to have only one poop per day, some even go only once every couple days. He could be gassy from the rice cereal you are adding to the bottle. And speaking of that, adding cereal to the bottle should only be done under a drs recommendation. Also, there is no proof that it actually helps the baby sleep through the night.
Your son is 4 months old, have you tried feeding him cereal from a spoon? My son loves to eat from a spoon and it has helped with his spitting up.
As for the night wakings, you could try getting him to go back to sleep without feeding. Some babies still need those late night/early morning feedings though. You should first check with your dr to make sure its ok for you to encourage your son to sleep through the night. My husband and I have a "rule" that if Cody wakes before 5:30 AM he doesn't get a bottle. If it's 5:30 or later he gets a bottle. When he wakes we just ignore him unless he starts crying. If he's crying we pat his back, give him the paci and he goes back to sleep within mins.
I hope I have offered some useful advice! Feel free to contact me if you want more info or details about any of it!