Have you at least tried brainstorming all of the options available to you, no matter how seemingly outlandish. The, actually thinking about them with a sense of possibility, rather than dismissing them at first glance.
Shall I start you off?
Get another job
Get a better paying job
Get a credit card to pay the attorney
House share
Get a job where the room is included
Live in your other house
Report your husband to the police re the gun so you have a paper trail
Let the house go to foreclosure
Or are you, as you have mentioned before, waiting for his liver to finally pack up, or perhaps for him to use the gun on himself so that all the financial problems will be resolved? Because I really can't believe that if you didn't want to go, you wouldn't have done it already. Despite what you seem to believe, you are in a better position than most on here. You have a job and no dependents. And no, your grandkids aren't YOUR dependents, they have a mother.
My sense of entitlement kept me stuck for a long time. I hope yours doesn't do the same. And don't forget, the things we get most angry about are usually those that we need to take a real good look at, because our subconscious is giving us a big hint.