I need to save myself - what needs to get done before I move on?

I posted here last July for the first time because I was struggling with how to deal with the needs of my dysfunctional family. I'm sure many of you dealing with these kinds of situations will not be surprised to know that little has changed. I'm here now because the situation really has reached its climax for me - either things change, or I have to find a way to leave ASAP.

Quick summary - both parents in late 70s, father has an autoimmune condition which causes problems with balance and walking and his "mind has started to go" (though he will never get tested). He has started to repeatedly fall for scams (nearly wired $500 to a scammer, got his computer hacked by giving access to someone over the phone, has gotten conned into giving ride to random person who then hit him up for money). You've never met someone in your life who has his head buried so deep in the sand - refuses to deal with reality. If anyone can give him a run for his money in that regard, it's my mother. After YEARS of trying, finally got her in to get tested and confirmed she has mild-moderate Alzheimer's. She's also as personality disordered as they come. Narcissistic, histrionic, obsessive compulsive, the consummate martyr and eternal victim. She's disgustingly emotionally manipulative and has made my life a nightmare. And my father has made it his life's work to enable her. My role is black sheep, scapegoat, and punching bag...oh, and the "adult".

About 4.5 years ago I moved "home" to get back on my feet after losing my job. What ended up happening is that I've gotten sucked into the black hole that my parents are. I've totally lost myself. I suffer from chronic depression and anxiety, and now add to that a level of anger that is absolutely killing me. I'm broke. I have no support from family, no friends nearby and those who were my friends have dropped off the map. And still I know, it can always get worse. That's what I'm trying to prevent right now. I really feel it's now or never.

Here's the deal. My mother's lifelong love and obsession and dysfunction is money. But the disease is catching up with her now and in the last 6 months she has started to forget to pay bills. Their cell phones were almost turned off the other day because she hadn't paid the bill since January. Every day is Groundhog Day, with her manipulating me into her psychodrama because she can't remember how to long into an account, doesn't know passwords, etc. I am so furious I refuse to continue like this. So I have put my foot down and said it is time for her to sign the POA and let me pay the bills. But she persists in her old ways and makes progress impossible. And my father will acknowledge privately to me I'm right, then five minutes later he'll be threatening to hit me and telling me to back off and leave him alone. They have no will, no medical advanced directive/POA, refuse to make arrangements to move to a community where they can transition to assisted living (which are at a minimum a year's wait to even get into). In my efforts to try to get them to turn over the bills, it has also become patently clear that they don't know what all their bills, assets, investments and insurance policies are. They don't know what they're for, can't find previous statements...it's appalling.

So I'd like to consider a hypothetical. What would happen if I left and left them to flounder? (Now, I'm not in a financial position to do this immediately, but if this is the best option, then I know I need to get creative and try to work something out). What happens when my mom's Alzheimer's worsens, her credit goes down the tubes, they haven't arranged for any care and there's no designated POA? Does this responsibility ultimately always come back to the children anyway? Because my fear has been that if I don't deal with this now, I'm going to have to take them to court later to get guardianship and I can't even stomach the thought. If all roads lead back to me, then I would rather push through now and figure out a way to get the POA signed at least.

Bottom line is, I need to save myself from this sinking ship. But once I've jumped ship, I don't want to still be roped to it. So can I leave them to wallow in their own mess, or do I need to get the POA and get them to commit to alternative living arrangements before I go if I really want to be free(er) of this and move on?