Seller refuses to seek permits for detached structures on property because it might "muddy the waters"

Forgive me for not using my main Reddit account.

Edit: Do I need a real estate attorney?

I'm under contract to purchase a short sale property- I'm paying well over asking price, outbidding multiple offers and probably myself. The property contains a main house, detached garage with guest suite, detached car port and detached shed. It's been quite some time and we're expecting bank approval any day now (As the amount offered is really close to what is owed.)

Due diligence has found that every detached structure on this property is over the limit for allotted detached square footage in this county- and a representative of the sellers (His grandson) has appeared before the zoning board multiple times only to be told to get the required permits within 30 days or remove the structures. Of course, they never obtained the permits, the board has ordered the sellers to remove the structures and they have not. The sellers owe over 300k in code violation fines.

In an effort to help with the already lengthy and frustrating short sale process, I'm willing to go in front of the board and appeal their decision as a potential future homeowner and seek permission to keep the structures if/when I purchase the home. These structures were originally brought to the county's attention as the current tenants are using them to operate a commercial business (amongst other illegal things). I would only use them to store my personal vehicles and lawn mower. All I need is the application fee to go in front of the board and the seller's signature on one page saying that I'm under contract to purchase this property. Although it would probably make his structures legal and the property actually sellable, he refuses to sign as it would "muddy the waters"- he's afraid it will blow the lid off of all the illegal activities that his tenants have going on there.

And well, it will. But he can't legally really sell/market the property at the price including all the structures without doing this. His "listing agent" is his "friend." The seller owns the real estate company his "friend" works for. His tenants are also related to him and his tenants' tenants are their grown children.

What can I do to move forward with this sale and get this mess cleaned up?

Edit: Before you all jump the standard r/realestate answer of "walk away," know that I'm willing to do what it takes. This is going to be my house.

Edit 2: Additionally, my realtor is at a loss for how ignorant the listing agent and the other parties involved are. I'm stuck.

Edit 3: This is a RESIDENTIAL property.