[Hershy]

Hi, kms,
I have been away for awhile, so am not up to date on all the discussion, but have you considered there could be a parasite present? That is, since you have tried many options with the diet? Coccidia is common and will cause a similar stool. Here is a link about it. The occurrence of this is most common in young puppies, but can show up in any dog.
This link has more information about it –
http://www.petmd.com/dog/conditions/infectious-parasitic/c_multi_coccidiosis#.UpoFpeC6_8s
Whipworms is another possibility- a link about that is- http://www.petmd.com/dog/conditions/infectious-parasitic/c_multi_trichuriasis#.UpoIG-C6_8s
As I said, this may be old news to you, but wanted to offer in case it isn’t.
Take care, and hope you are able to solve his problem soon.