The point of the prevacid is to help with any pain and to stop acid production to prevent/heal esophageal damage. If you don’t feel that your son needs any of those, then you can decide from there. Maybe he’s fine on zantac, or maybe he just needs prevacid. Most babies don’t need both b/c a good dose of prevacid kind of defeats the purpose of the zantac.
As for his dose, dosing is weight dependent, but it definitely sounds like a good high dose. If you want to start lower and see if that makes a difference, some people go that way. I personally like to start high then taper off.
Good luck with your decision.