Wow, Does this all sound familiar to me!
When Molly was about 6months we had TONS of testing done because her stool was just like water, and she couldn't control it-going in her crate and very sad about it
We tested for about everything my vet could think of, pancreatic problems, blood work, parasites etc. what we ended up doing is adding 2 tsp of metamucil to her food 2x per day and is it ever like night and day....which is strange you would think it would have the opposite effect! We even tried to wean her off of it in the Fall and she went back to watery stool, back on the metamucil and she's back to healthy stool!