That is a fairly open threat.

Now we have a possible real threat in Iran.

F. invited C. to move upstairs with him, but I refused to have C. remain a resident because of her threats and her overall response to me.

What you need to do is identify what the threats are and what the best solutions are to mitigate those threats. 

He probably has multiple people chasing him for money and in those cases, people only deal with the biggest threat to their business.

Next talk to a Real Estate Attorney and should the threat of the seller backing out becomes real then have the Real Estate Attorney send a letter threatening to go to court to sue for Specific Performance.A Specific  Performance case would tie up the property for years. 

Obviously, the threat of lead based paint is there.

Threats are actually a relief since 99% of the people who make physical threats are too cowards for any physical confrontation.

There have been threats by relatives but they are rare and I have not had one in over a dozen years.I think the information given out here is wonderful, the only possible thing I would add is that awareness of your environment is very important.

We have: the NSA cyber command that is transferring to Fort Gordon, GRU is expanding, the medical community is booming, Starbucks is opening up a new factory here.