So sorry, Monty and Dew, to hear that you guys have been put out with all of this and the grandkids are stuck in the middle of it. It's so hard to watch your loved ones make bad decisions and sometimes not know what to say or do to help or at least not run them off. Sometimes, many years later, the kids come to realize they wished someone had tried to talk sense into them. Seems like the boyfriend in your house will be the easier situation to fix. I'd not let him stay either. Visit, maybe. And you have to wonder what's wrong with the other daughter's head to want anything to do with the mess with that criminal. That I would have to be saying something about. Could wear yourself out trying to talk sense into her. My brother has been that way. A lot of long talks, he listens pretty well, nods his head and goes right back to what he was doing, only to return and complain again that he doesn't like the results of his actions. So frustrating. There could be a lot to regret later should anything happen to those children. Maybe both children should go live with their dad until that guy is gone. There should be plenty that can be done to make that happen since it will be easy to prove to authorities that they are in danger.
I had to move back in with my dad a couple times when I was in my teens/early 20's until I got everything figured out. I'm thankful that he helped me out. But I'm sure I did wear him out with my late hours, working and staying out too. You should expect her to be pitching in on what she can, household chores or whatever. My DH and I stayed with my inlaws in the MIL apartment they had adjoining their house. It was a separate unit, but still close enough proximity that we sometimes annoyed each other, but overall we got along fine. We helped with both chores and utility bills too though. This was while we were saving a down-payment for our house, 3.5 years there total. Then when we moved out, they didn't want us to go! LOL. They got a little nibby in our business by that point. All in all, I probably wouldn't do it again, just because it is healthier for the parent/child relationship to get out and be on your own.
I hope things get sorted out and less stressful for you guys soon!