Why is it so hard to leave? Let's see... some possible reasons:
Right now, as bad as the situation is, you know it and understand it. When you leave, it is a great unknown, and the unknown is always scary.
Maybe you still care for John.... I don't know. But I know when you see someone you care about walking a destructive path of life, it's extremely difficult to walk away. You want to stay and help that person, even though you can't fix a problem that doesn't want to be fixed.
You're worried about being the bad person by taking the kids away from their Dad.
I don't know if any of those are true.... I'm just offering some suggestions. It IS hard to walk away.... I know in my case, when I walked away from an abusive ex, I thought I was a failure for not being able to make the relationship work. Of course, that's silly when I look back on it, but.....emotions are tricky.
You MUST leave though, because the situation is unhealthy in every way for everyone involved including yourself, your kids, and your pups. Once you walk away, you'll wonder why you took so long to do so.
Here are some strength vibes to help you on your way!! {{{{{STRENGTH}}}}}
Let us know if there is anything we can do.