My 5 month old son has reflux also--hang in there, I know how frustrating it can be! It will get better, but making it better for each baby takes a lot of experimenting for what works best for your child. My son also screamed A LOT and didn't sleep well. Like you, we tried Zantac first. It helped a little, but not as well as I thought it could, like you.
My recommendation: you didn't say if you've seen a pediatric GI specialist, but if you haven't push your pediatrician to send you. The general pediatrician is not a GI specialist, and mine admitted that they just try a couple approaches that have generally worked well. A GI specialilst will be able to listen to you about your sons specific symptoms and perscribe a specific course of medications to help! It made all of the difference in the world for my son...we ended up on Prevacid in the am and Pepcid at night and after a week of watching him get better and better as the Prevacid kicked in, life has been much better. And I did a lot of internet research about cereal in the bottle and a lot of research indicates that it does not improve reflux symptoms.
Good luck to you! I promise it will get better!!