Unfortunately the only legal recourse you have is serving him
with eviction forms and then filing the eviction if he doesn't
pay or vacate. For better or worse, squatters basically have
the same rights as tenants when it comes to ejecting them.
As for the threats of damage, there are several ways you might
tackle that. First, I would record the threats if possible, as
evidence. Second, I would inform the judge in rent court of
the threats. Third, you may have to sue him in small claims
court to actually win a judgment for those damages, unfortunately.
Fourth you could call the cops on the stupid junkie.
Anyway best of luck, fill out some eviction forms and serve
the guy immediately, and good luck getting him out!
Eviction Forms