LW, so at the way your family is bullying, bribing and threatening you! You've said they can stay friends with him, with your blessing, so their relationships with your rotten husband are not threatened at all. It's YOUR relationship with him that is changing, therefore YOUR business. I would tell them nothing more, they don't deserve to be involved.
All your mother's talk about how hard it's going to be is c**p - this will be as hard as it gets, and things will get better once you're out of this situation. Yes, you might be financially stretched, possibly lonely, but you won't be questioning your own decisions, abilities and loyalties like you are now.
I have an analogy that has helped me get through quite a bit of stuff, and it might help you too. Think of this situation as if you were taking a bath - you've been in the bath (your relationship) for a while now, and the water's pretty cold. What you should really do is get out - but it's colder OUT of the bath than it is being in there, and everyone's saying 'ooh, you'll be cold if you get out'.
Yes, you will be cold - but then you'll get dry, you'll warm up, and you'll move on. Sometimes you've got to do something painful or unpleasant to get to the next step, and YOU are DOING it.
Stay strong, and get out of that bath! We all think you're amazing. xx