HELP FOR THOSE WHO CARE FOR DISABLED DOGS

Mom to 12 year old Old English sheepdog named Riley. He was diagnosed with EPI in June, 2013. Currently takes 1/2 teaspoon tylan twice a day, and is also on Metronidazole twice daily for Sibo, B12 reigning and gets Panakare enzymes (1/2 tsp per cup of food) with every meal. In addition to EPI, he's had a multitude of health issues. Takes daily thyroid medication for low thyroid, has sebaceous adenitis, and arthritis has progressed with age.  DM looks to be what is going on with his hind quarters now.