I'm so glad you asked! First of all, it doesn't work to feed them baby cereal to help them sleep better because filling up a stomach before sleep makes one uncomfortable. Even worse, when you're talking about such a young infant, whose digestive system is nowhere near mature enough to handle anything other than breastmilk or formula, it can be even worse, so they'll wake up more.
Besides that, feeding a baby anything other than breastmilk or formula before 4-6 months (preferably later, like 6 months) will put your baby at risk for food allergies. Please just wait. This is the difficult period when your baby just plain needs to eat frequently, with a small stomach in a small baby body. As they say, if you cut corners, you'll just end up going around in circles. So I'm glad you asked and your baby will benefit from your waiting to feed cereal and other solids.
You might also want to consider stopping hte rice starch for this reason, as well. I suspect that the reason your baby appears to have acid reflux is, he's actually probably being overfed (like many babies who are formula-fed). Unfortunately, the guidelines provided by the formula companies favor their profit margins more than the health of babies. Basically, if you're feeding the baby more than he needs, it means you need to buy more formula, which pays the company more money, of course. Then, the baby spits up because he is overfull. Then, you feed the baby more.
On top of that, the bottles - even the slow-flow nipples flow too fast for babies so young, so they seem to ravenously gulp down what's in the bottle, and so they get overfed, because parents think, oh, he is so hungry.....
So, what you can do is take breaks frequently when feeding your son, and feed him less. The nutritionists recommend that they get as many ounces as they are old in months. So, give your son 2 ounces per feeding, and feed it to him slowly. Remove the nipple any time that he seems uncomfortable or confused or overwhelmed in any way. You will probably see the "acid reflux" disappear within a few hours!
L.