I had them reduce the price by the estimated asbestos remediation quote ($55K) as well as do a seller lease back for a full year.

never a thought to the cost of demo  lead and asbesto's remediation dump fees etc etc.. so lot value is usually 50k less with a tear down on it. 

A simple operating agreement can remedy this for most lenders. 

We usually get a courtesy notice the first time, then are given a few days to remedy.

Looking for any insight on how to remedy this (reached out to VRBO and Guesty with no solution yet)!

If neither of you have keys to the unit, that is definitely something to remedy immediately.  

I plan to remedy the issues and place a tenant.

We got an email last night that the buyers financing ran into a "glitch".We are told they are seeking another lender, but are waiting to see if their lender can remedy the situation... however they are confident we will not close in 4 days as previously committed.

I wouldn't close on a house with a CO, or without at least a temporarily CO detailing whatever may be required to get a real CO (like if you're buying a house under an agreement and understanding that you'll remedy or pay for whatever issues the house may have).

If he didn't finish the job, I wouldn't pay him another penny until he does -- you've already paid 90% of the job, and I wouldn't pay the last 10% until the job is completed.As for the extra $5300, that's up to you if you want to pay it or not, and if you want to risk the contractor not completing the job (if he hasn't already) or potentially putting a lien on the house or taking you to court (both of which you should be able to remedy if you have a reasonable contract for the $31K price).Long story short, consider this a good learning experience, and be sure to clearly define payment/draw schedules in the future, along with a clear process for change orders.