Ugh - this is horrible! So sorry!
Most everyone has helpful advice, but the truth is sometimes the only thing you can do is make your area into a safe sanctuary. We've been through a similar situation with an irresponsible dog owner.... talking, then pleading, then police, then animal control. The final word was that until the "next time" there isn't much that can be done. I'm guessing that as a tenant you won't even get this far without making your life completely miserable.
Shooting the dog would have been the best option for us - but irresponsible dog owners tend to get more dogs. The right kind of person (wrong kind?) will also retaliate if they're held responsible for anything, as we've found. So.... sometimes you have to do what you have to do, regardless of how "unfair". Move if you can or accept that "it is what it is" and keep your animals out of this person's way.
Too bad life isn't more fair.
At this point I don't think the chickens are the main concern even though it is very wrong. I'm really concerned for her safety. It's no longer an issue of a dog. If she does not get authorities involved and he continues to escalate she could be harmed. I think she needs to try to protect herself and the police can advise her the best way to do this.