Is there anything in your lease or rental agreement about not conducting a business from the house?
Post a Cure of Quit about the late rent in accordance to your state laws.
Did you do an inspection and post a Cure or Quit notice about 1) not using the rooms as they are to be used i.e. a basement is not a bedroom, a kitchen is not a bedroom, etc. 2) garbage in the yard 3) yard not maintained (if it's in your lease and its not under snow...or did these matters come to your attention once the rent was late?
Make a police report about the threats. Encourage the neighbors to make a police report as well.