He even had the audacity to try to manipulate us into signing an agreement waiving our rights to go after him in court.Earlier this year, several larger investors forced MBD into involuntary bankruptcy (case 2:22-BK-16483-ER, U.S Bankruptcy Court, Los Angeles Division).

You can sign a new lease with your new tenants, but I would say you should honor the lease rate of your tenant still under lease… but definitely have them sign your lease because without it you have no agreement with them between you and them.  

The best case deal for us would be to find an investor who is willing to buy the land and do a 10-year (or longer) rent-to-own agreement with us that includes them getting proceeds from the campground and event center and making a great profit over time. 

But you can offer a "buy out" agreement to the tenant, and yes, 2 months' rent value is commonly seen.

I would review my loan agreement - as the bank must abide by the terms within that.  

I wouldn't enter into a partnership, but would suggest a JV agreement drafted by an experienced real estate attorney.

Also, if you have a partner(s), get a good operating agreement that outlines financial liabilities to limit your personal cash input.

We have been talking to a few property management companies and all of them seem to have astronomically high fees and very tenant friendly management agreements. 

Started yesterday after I sent a lease agreement to new tenants.

@Paul De Luca and/or @Jonathan Klemm - would you be willing to share your Chicago-specific lease agreements or what language you use in your leases for the early termination so we can incorporate that into our future leases?