It would affect DF similarly as the field he is in grad school for is one involving government security clearances and having a sketchy past would prevent him from ever obtaining a high level position and current allegations of drug use would get him immediately kicked out of his program, no questions asked.
Wow, so even an unfounded allegation would get him fired? That's wild.
It depends on how it is approached, but basically, yes. Allegations of illegal activity are considered unacceptable and while they are supposed to look into these things, they usually don't look very hard. People in his program have been kicked out for less. Apparently they have this story that circulates at the beginning of every year to the new grad students about a guy who broke up with his girlfriend and she got back at him by going to someone fairly high up in the food chain and saying that he regularly drove drunk and was an alcoholic who had guns without a license. Because it came from someone so close to him (and the story says she put on a good show), they really didn't pursue it and he was kicked out. No idea if this is true or just something they say to scare people, but that is the environment there. I have to think that if someone was wrongly kicked out, they'd be able to get back in somehow if they could prove it, I'm not sure if that would involve lawyers or something else, but would surely be a lot of hassle and time and money.
So yes, I'm probably panicking over nothing, when I realized the potential consequences I think my brain went a little crazy, and I appreciate the reassurances and pulling me back down to earth.

I will definitely contact my landlord. I think we'll hold off on anything work related because there's no point in creating drama that doesn't need to be there. I may call the non-emergency police and see what they say about it. She makes me so mad every time I talk to her, so I think maybe ignoring her completely would be the best choice. No need to get my blood pressure up over some grouchy dingbat.