He sounds like a bundle of joy! Just a question? Could the runny poo be from what's called giardia (not sure on the correct spelling)? Our vet said it is small microscopic worms, usually gotten from other pups, like when they walk in it, etc...Angus and Roxey both got it awhile back, from school I'm guessing. Don't know if your vet has checked or not, just thought I'd pass it on.
Anna