I would report them to HUD. There is so much about this seller/agent that is troubling.
If you have the wherewithal to close the deal, that is all they need to know. The agents should not be allowed to get in the way of any deals. The fact that they try (“special” relationships with certain agents, unwillingness to work with certain agents, etc.) means they are not representing the best interests of their clients.
File a formal complaint with HUD and copy the listing agent, the bank/lender, AND the seller directly.