Hi - I think you are doing the right thing with respect to finding a better food. One of my dogs has had a sensitive stomach her entire life. I use to take her to the vets so many times to get the same meds you are describing and more. I was told she had gastroenteritis and was encouraged to change her food to a perscription brand. I had her on Eukanuba low residue but it wasn't until I switched to Orijen that I saw an amazing difference in her. This is a dog who seemed to throw up almost every week. Since she has been on the new food she has not thrown up once in 10 months! This is really amazing for her and I would definately look into a better quality food if you have ruled things out in the medical departement!
If you feel there is a problem with chicken, Orijen is also coming out with a fish formula soon and are rumored to be introducing some new formulas next year. But if you take a look at the food forum, I'm sure there are many that could help you find a better quality food. It might take some time to figure out which one works for you.
As for the sulcrafate - I think I just wrapped it in a small amount of cheese and didn't dilute it. 5ml is not very much water so maybe it was just a method for helping him swallow it?