He illegally threw me out of my apartment and pulled a gun on me to threaten to kill me. 

Threaten to report him to the BBB, and review w/ Yelp, Angie's List, Google, etc. if he doesn't drop his demands ASAP and leave you alone.   

He then sent us an estimate via email, but no contract, despite us asking for one. 2.5 weeks later the job isn't complete, and when we told him we can't wait any longer and will complete the work ourselves, he called us ungrateful and threatened to file a lien.

He may just be testing you, why not pay a couple hundred bucks for a strong attorney letter threatening suit for specific performance if he backs out, his reaction may be different if you show you are serious.Lawsuits are not fun and because you plan to live in this property you have to decide how much stress you are will to take on before even taking ownership.

I think you already have some great input from @Joel Owens and @Jeff Filali but let me say a couple of other things.The people that think commercial real estate are threatened by technological innovation are very limited in their thinking.

He threatened to take a hammer to the job and wound up having a sheriff standby to see him off the property.Never again

And get ready to hear them ***** incessantly about damage they do, and threaten to call section 8 if you don't fix it.

The difference between me paying for groceries and me paying for taxes is that I willingly paid for groceries, I was not threatened.

Feds threaten man on oiled Florida beach: "ILLEGAL TO DIG"

Just today, Moody's has threatened to reduce the United States credit rating to AA.An article that I just listen to furnish by Keith on another post was even more scary.