I'd really vet the developer, their past projects, talk to prior partners (GP & LP) to see how prior development deals worked out and how the communication was, etc.

GP's going dark on the LP's, no response to communications etc.

So, communication and assignment issues, as well as not being able to explain the maintenance issues and the required work.3) Proper documentation and quality of work issues.

Start by clearly outlining your renovation goals, and follow up with an in-person or virtual consultation to ensure both you and the contractor understand the vision for the project and expectations.

To date all I've received is email communications from the sponsors stating the deal failed.

Document every communication in writing!

A small number of minor picture hanging holes or command strip usage on a wall is not unreasonable and would be considered normal wear and tear virtually everywhere. 

We get just as frustrated because the system is a bit "broken":(I believe the team is in communication with you about your options - just be sure to also let us know your choice to secure the property to deter squatters as cost-effectively as possible.

-So, I'd only be willing to pay you a flat fee for that service that is CHEAPER than an attorney.2) Negotiating Price: theoretically, I can negotiate myself and MAY just need someone to communicate my offer(s) to seller.

I think communication seems to be the issue here especially with your comment on how the PM is unresponsive.