Tenant B replied that he was tired of “this” and that he wanted his lease terminated because he feared for his safety.

We offer early termination for basically all leases, which is 1 month plus the deposit if there's no damages. 

Smoke detectors, missing batteries 6.

I would consider 12-18 months short term in a buy and hold investment.  

Like Caleb's response, in Florida, a landlord can't terminate a specified lease term on grounds the the landlord wants to sell, unless the lease provides the landlord with that termination option.

Last December I had a tenant terminate lease early.  

No exceptions.They can either figure out their issues and abide by the contract, they can terminate and pay the penalty, or they can face eviction.

In my area, an inspection contingency means as long as you have a licensed inspector actually inspect the property, you can then terminate just by sending a release/termination, even if nothing major found.

Also, title doesn’t change hands and if they back out, there are no refunds - they just terminate their lease and away you go and find another buyer.  

If your lease contract is much more thorough and comprehensive than the lease they're on now, you may want to try having the current residents sign a new lease using your contract (you would probably need a mutual termination agreement as well to void out the existing lease; again, I'm not a lawyer, so definitely worth consulting one!).