So I've been house-hacking for about 3 weeks when this happened last weekend. I'm still going through the trauma but I would very much like to get the legal requirements of this situation over with as soon as possible.

My roommate passed away and wasn't discovered until days later. I've told the sister who claims to be handling the estate and has collected his belongings that the cleaning service costs well in excess of the $500 deposit. There are some holes in the wall that haven't been repaired. Even after paying a company nearly $1,400 to decontaminate and remove the smell they quoted me another $400 to ozone treat it. I instead went on amazon and spent $110 for my own ozone machines. 

I understand I need to mail a certified letter, but to where and to who? Do I mail it to his name's estate at his drivers license address? He had only been my roommate for 3 weeks before this happened.

I have no intention of going after the family for that but the sister doesn't seem to understand that they are not going to be getting any money back from me. That the costs of this situation are so far in excess of the security deposit and last months rent it is just crazy.

I'm assuming if I do manage to get it cleaned up and rented out in time before the last month expires that I need to return the money to them. Is there a way I can use that to make up for the lacking security deposit? I have no plans on going after the estate, but I also don't want to say something that obligates me to give them a large chunk of money if I otherwise wouldn't have to.