Although Vivian did essentially (and reluctantly) give permission for Hutch to even the score, I don't know if he will. He doesn't seem like he has it in him, and if he does, he's not in the frame of mind for making something happen at the moment - unless Addison's hints are genuine and she takes advantage of him under the guise of a "pity fuck".
With regards to Addison and Christian, I'm actually edging towards it being her mother in the bed. The wording I posted earlier made me think that it could have been a deliberate choice. If Christian said Addison was his niece, we wouldn't know just from that whether it is a brother or a sister of Christian who is Addison's parent. By saying "my brother's kid" though, it tells us that it is not Christian's sister (if he has one). That could leave it open for Christian to be fucking his brother's wife, Addison's mother.
I could definitely see Christian being the type to fuck his brother's wife behind his back (or not even behind his back, perhaps). In terms of the late-night phonecall we see, it would be less likely for someone's wife to have a sleepover than his daughter to have a sleepover, but that could be explained in many ways (girls' night out and slept at a friend's house, the husband is away on business and so wouldn't even know his wife isn't at home, etc.).