Glad he's feeling better! We were having the same issue with Revy - chronic diarrhea and very dry fur with lots of flaking. The boiled meat and rice, nor pumpkin was helping. The vet put us on prescription Iams food (Iams kangaroo and oatmeal) and said NOTHING ELSE. When we finally listened to her, the diarrhea cleared up, her coat looks better and she's gaining weight again. It's been a week of consistent poops and I'm thrilled. The last couple of days we've given her a small amount of dehydrated duck treat and also crump's sweet potato treat for training and the poops have stayed firm, so that's a relief.
Like you, once we are through this bag I'm hopeful that we can transition her to a better quality food. We think she seems to be sensitive to beef and rawhides, but it'll be a case of trial and error to figure out what she can tolerate and thrive on, I think. We suspect duck and sweet potato will be the key, but we'll have to see. We are just happy that we didn't have to put her on tylan powder to resolve the issue.
All the best to you and Ranger.
Revy: Female GSD born March 27, 2013
Sweetie: Female black cat, born 2004
Plus a husband and a couple of teenagers