In this scenario there is no such relationship... the adjustment, if it occurs, will require 3 parties to cooperate.

I'm trying to get all the emails, text, and documentation from the listing agent that they have from the impersonator but, they're not cooperating with me. 

It means that people in a team, like a sales team, cooperate and help each other to achieve common goals.Imagine you're in a relay race, and each team member runs a part of the race before passing the baton to the next.

(d) Cooperation of Secretary and executive departments and agencies in administration of housing and urban development programs and activities to further fair housing purposesAll executive departments and agencies shall administer their programs and activities relating to housing and urban development (including any Federal agency having regulatory or supervisory authority over financial institutions) in a manner affirmatively to further the purposes of this subchapter and shall cooperate with the Secretary to further such purposes.

Which makes sense because by cooperating with other people you have way more leverage to accomplish more through increased knowledge, capital, systems, and network.

They still need to reveal any material defects known to them, but otherwise are very limited on what they can say or do.As a typical Buyer (which is likely your status with "inactive" license, but check your local RE licensing laws) if you are comfortable with the overall sales process, you can certainly use the listing agent (usually they are able to help you complete a standard purchase offer) and you can also negotiate the "cooperative" side of the commission.

We have a 2.75% rate and would love to hold onto the property as it continues to gain equity/making money via short term rental.1) Would you walk away at this point knowing you have nothing to lose and have already been cooperative with the buyers who are not pushing on their end to get their lender to close?

Someone who buys a property with probate title problems and a non co-operative heir, is either a gambler or a very patient buyer who wants the property badly enough to put up with the hassle or doesn't understand the problem.

Normally the seller can just give the bank authorization but the seller is completely unresponsive and not cooperating.

They're going to cooperate 0% is my prediction.