Hello!
I went through this with my son, who is now turning 2 this month. We went to see Dr. Argao, who is a pediatric gastroenterologist and was great. He really worked with us to find something that worked with my son, and everything he suggested worked for us. My son took Prevacid, which helps with the burning sensation but does not decrease the reflux itself. Dr. Argao put him on a medication called Bethanechol, which is actually a medication for something else but helps move things through your digestive system so that there is not as much to reflux. This really made a world of difference for my son, so you may want to ask about that and see what your dr. thinks.
My son had pretty bad reflux, it would come out his nose, we were changing my clothes and his clothes several times a day, and it was really hard for both of us. We never found a cause in terms of food or anything, and we never did any of the invasive testing that I know is sometimes recommended. Dr. Argao said that many babies outgrow reflux when they start to walk since they are spending most of the day upright, and this was true for us. If at that point there was no improvement, he would have recommended some of that invasive testing, but it was not necessary in our case.
So I guess I don't have any good suggestions on questions, other than asking about Bethanechol. I just want you to know to hang in there and hopefully it will get better as quickly as my son's reflux did.