I’d simply fire him and not be concerned about any “threats”....you can’t be scared of morons or scumbags. 

Completely ignore the threats to put a lien on the property2.

He started threating to get a lawyer involved claiming there were things we didn't disclose about the house, which is nonsense. 

I still use travel agents from time to time, because it is much easier and only a little more expensive.And that is the key, of course, and the biggest threat to the current realtors.

What she says she does is highly illegal but she is not in threat of any legal action because she doesn't actually practice what she says.For those who don't know, the investor claims she buys homes falling apart and then puts illegal immigrants into the home and makes them do the repairs on top of charging each person $400 per bed.

//Begin Gain From Involuntary Conversion Rules(c) Conversion into money or into dissimilar property.(1) If property (as a result of its destruction in whole or in part, theft, seizure, or acquisition orcondemnation or threat or imminence thereof) is compulsorily or involuntarily converted into moneyor into property not similar or related in service or use to the converted property, the gain, if any,shall be recognized, at the election of the taxpayer, only to the extent that the amount realized uponsuch conversion exceeds the cost of other property purchased by the taxpayer which is similar orrelated in service or use to the property so converted, or the cost of stock of a corporation owningsuch other property which is purchased by the taxpayer in the acquisition of control of suchcorporation, if the taxpayer purchased such other property, or such stock, for the purpose ofreplacing the property so converted and during the period specified in subparagraph (3) of thisparagraph.

This sounds like it could be a "Triple Threat" scenario given our backgrounds. 

From what you have described, I don't think he will stop, but if you begin with that first step, you've at least left open the possibility of him realizing his mistake and correcting it without threats which are going to cause the relationship between you and the tenant to sour, make your living situation miserable, and encourage him to trash his unit or create other problems.

Even if you're 110% honest and up front, there will still be questions, maybe hard feelings, and hopefully never litigation/threats/etc.

Sounds like you need a restraining order or at least the threat of one.