I don't usually post on f and f but the comment about staying in the marriage to provide damage control for a 14 year old by explaining the rants of a self-absorbed drunk...nah. That just won't work. The rants will happen with or without you and kids don't listen as much to what we say as to what we do!
I think we would all be utterly floored if we knew just how well our kids understand us, our marriage, our various train-wrecks.
Are they going to listen to us explain, anyway?
Is a kid better off living with a parent that has to be explained, or living free of all the dysfunction, without having to experience the burden of it? I think you've gotten a lot of good responses about that...