The symptoms sound like TriTrich to me, which requires Ronidazole as a treatment. I wasn't able to fork out the money for the test, but I tried every treatment from panacur, metronidazole, pumpkin, diet changes, working with my vet and that was the only thing to cure him. My struggle went on for 4 months until he finally got well for good after the Ronidazole.
Some of the telltale signs of TriTrichamonas is a leaky butt, and terrible smelling poo. Keljin was not cleaning himself either, I literally was following him around and wiping his butt drips every 5-10min and cleaning everything..
I'm sorry and feel your pain, I hope little Thor gets well soon and that you and the vet figure out what the issue is!