Yes, my boy was finally diagnosed as having Lymphangiectasia. Rudy's symptoms don't match what I saw. You seem to have more vomitting, we had month and a half long diarrhoea. We had vomitting at the start though. I'll look up my old threads in case it gives you any clues that might help Rudy.
Loose Stool on Rice and Boiled Chicken?
Inflammatory Bowel Disease?
Folliculitis
Nutriscan Results for Oban - Food Sensitivity and Intolerance
Lymphangiectasia?
Endoscopy NOT Done and Oban is Home
I Can't Give B12 Injections Myself? Why Not? Did/Does Anyone Do Their Own?
YAY! Albumin up to 22
Liver Support, Milk Thistle - NO Flavouring Added
Oban Update - Good News
Oh my gosh, what a lot of links. The first ones were the discovery stage for us and are long but contain posts from folks here offering suggestions and talking about an experience with their dog and what they did.