Best way to get your answers would be to send your questions to Shaykh Kabbani’s Khalifa or a mureed from the tariqa.
As for this part of your post,
“Right, so if Sheikh Hisham isn’t a perfect human being and he can make human errors then does that give him the right to be a murshid who has hundreds if not thousands of followers who aren’t allowed to question what he says or does? What if he makes a fundamental error when it comes to islamic teachings?”
No that just proves that he’s a human and not a prophet or more than the prophets, I have no knowledge if his mureeds are allowed to question him (I don’t think any mureed in any tariqa is allowed to question his murshid, out of respect) but they are allowed to leave his tariqa if they find any error in him.
Also, what he said about wahabis being in control of most mosques wasn’t entirely wrong either.
We don’t know his intentions and unless we hear something solid with a proof from other scholars aagainst Shaykh Kabbani we shouldn’t be talking about this, so no more posts from me on Shaykh Hisham’s actions.