well, its been a few days now and i've been gradually mixing the Wellness small breed kibble into his Medi-cal gastro food and he's been gobbling it up! His stools are good/regular and he is CRAZY to eat (which is so unusual for him -it's a delight to see).
So far so good with the Wellness...i expect to have him eating it solely by mid next week. It has no meat by-products, no grain, no preservatives...I hope this is the answer to his life long gastric problems
Thanks everyone for your input.