Goldenseal is the world's most powerful antifungal and bacteria herb. He's gut is so senitive because of the infection. If he is that bad he wont live to see the so called cure in 10 to 15 years.
Try flushes with Oxypowder or even vitamin c flushes to lower the bacteria load in his intestine. Then give him a fecal transplant.
I don't know who told you probiotics don't work but fecal transplants are the only thing working for Antibiotics resistant in the intestines.
You can do a Fecal Transplant at home very easily. It is just a enema with poop.