Overwhelmed with Diabetes + Tiaditis

Hello everyone! After reading some of the threads on here about diabetes, I was impressed by how knowledgable and helpful everyone seemed. I decided to join in the hopes that some of you might be able to give me some MUCH NEEDED advice!

I have a 16 year old cat, Pika, who was diagnosed with both diabetes and triaditis a few months ago. We first brought him in because he was vomiting every day. He was diagnosed just with diabetes at first. We started his insulin (1 unit, twice a day) and got him better food. He had already been on wet food, but we got fancier stuff with higher protein.

He kept vomiting, so the vet did more blood tests and told us it was probably pancreatitis/triaditis in addition to the diabetes. Our regimen since diagnosis has been B12 shot, insulin, pain relief, and subcutaneous fluids. Unfortunately, Pika is still vomiting at least once a day. He doesn't seem completely miserable, but he is not as perky as he used to be. He is still eating and drinking, although I am not sure how much food he is actually keeping down. He often vomits a large amount. Sometimes it looks barely digested even though it has been hours since he ate. 

It is horrible to watch him throwing up every day. We were hoping treatment would relieve some of the symptoms of his condition, but it's hard to know how much of a difference any of this is making! He still seems like a happy cat, enjoys cuddles, still has an appetite, etc., but he is obviously very sick. 

Has anyone else had such a tough case? At this point, we would try anything if we really thought it would help him. He is a member of our family!

Thank you in advance for any advice. 

My cats (Pika on the right):

For diabetes, I believe that low carb wet food is the best diet. For pancreatitis/triaditis, did the vet mention prednisolone? It's commonly prescribed for IBD. Also, you might need to play around with diet. Some cats with pancreatitis do better on a lower fat diet. He also would probably benefit from smaller, more frequent meals. I would encourage you to check out www.ibdkitties.net which is written by one of the members here. There's a lot of great info there including triaditis.

Oops, I just remembered that developing diabetes from long-term use of pred is a concern, so maybe pred is contraindicated if he already has diabetes? I don't know but that may be why your vet didn't mention it.