Angry With My Partner's Father

My mother-in-law moved in with my partner and I this past weekend. I don't have a problem with this; she and I get along great, I love her and want to help her any way I can. My problem is with her husband.
Five years ago he left her for another woman, but that relationship has ended and he is living by himself. My MIL had been dependent on him for over thirty years before the separation.They did everything together and worked at the same place, so when he left, she had to learn a lot on her own. She has come a long way though. She got her own car; she never had to have one before since he drove them all the time. She kept the house up herself, mowing the one-acre lot they lived on, and managed the finances, although she did that before also. I am proud of her gaining independece and being a stronger woman. She wants to get a divorce but won't start the process due to her belief that the man should it.
Lately, Troll has been stringing her along, promising they will get back together once he gets them a new home. Since he moved out, she has barely been making ends meet and lost the house; he stopped helping her with the bills. His last promise was them getting a home together, but when the time came for the move, he changed his mind and wanted to put the new house in her name, which meant he wasn't staying and she would be in the same predicament. This all went down last Thursday night, so my partner and I were notified of the new situation that night and she had to be out of her house in less than two days and we had to paint the room and put in new carpet. We had already offered her the spare bedroom if she didn't have a place to stay, so she took us up on the offer.
On moving day, Troll got three of his friends to help them move most of her things into storage and the rest in our spare bedroom. He paid his friends with a nice riding lawnmower, washer and dryer, and other stuff and they repaid him by leaving after a few hours without the work being done. Of course Troll hurt his back a few days before and was having touble moving the rest of her stuff. Being the nice guy, I offered to help him move the last load; my partner and I drove out to meet them at her home she was moving out of. I promised my partner I would keep my cool and not say anything to him about  the situation. I only cared that my MIL was taken care of. Lucky for Troll everything went smoothly and I smiled inside every time he complained or groaned about his back. I can't beleve I held my tongue, I was so pissed.
I feel like I should say something to him. I don't want to start a fight or show off how bad I am. I'm not. I just want to get across to him that he will not get away with this. How is it okay for him to stay married and still do whatever he wants? It's not okay and it's ******* me off that he's getting away with it. No one will confront him about it. It's not fair to her. It's also affecting my partner though he denies it. He and his mom argue a lot about it and I'm getting tired of it. My partner is also tired of it; he wants them to get a divorce already. He wonders why she doesn't stand up to him yet he won't talk to his dad about it. If my dad was doing this to my mom, my brother and I would have already kicked his ***. But we're all different and Troll is not my father.  I see both sides and agree with a little of both, but I'm tired of being stuck in the middle and holding my tongue.
Maybe I should stay out of it, but I feel like it's my problem too, since she is now living with us. I've already made it clear to the household that he is not welcome in this house. I feel like I should talk to Troll and explain to him how everyone feels since no one talks to him about it. Am I wrong in this? Should I keep my mouth shut? I hate to see someone get taken advantage and walked all over and it makes me mad to see my parnter and MIL take out their anger toward Troll at each other. This is unhealthy.d
Jesse75 Jesse75
31-35, M
Jul 16, 2010