Yikes!

but don't worry:
Unless you've adopted her, she's not related to you legally, so if you become incapacitated, your husband or your own children would be the ones to pull the plug!

Family law & wills & advance directives & powers of attorney & survivorship & estates are so complicated & vary so much from state to state that you really *must* talk to an attorney.

It's very important that you talk frankly with those you designate to make decisions for you;
you don't want them to be unprepared, you want them to know specifically what you want, & you need the documents to make darn sure that they do it.

I've seen too many instances where "the family" *knows* what mama wants, but they don't think that they're comfortable with that, so they do whatever *they* are comfortable with.

I my own self would not designate any one person, including my spouse, for everything:
firstly, it's too much responsibility.
secondly, it's too much power.
thirdly, you are not the mother of all his chilren;
in a crisis, people are vulnerable to influence & manipulation.
A step-daughter's best interests are not the same as yours, & it sounds like her mother may have a lot of influence over her, & she would have influence over your hubs.

It's a good idea to split up power & resonsibility so that pulling the plug doesn't equate to the plug-puller winning the lotto.

Once you've learned all you can from an attorney about protecting your own interests, you & hubs need to consult one about your mutual concerns.

If he is incapacitated, who decides to pull the plug?
Who inherits what?
How can he execute a failsafe will?
How can you be sure to have enough money available immediately to pay bills?

Re-reading your post, I'm struck by the impression that stepdaughter sounds depressed.

Feeling empty, not loving people, not looking at you, etc.

Please don't be shy, & don't allow hubs to be shy, about bluntly, in plain language, pressing her doctor about this.

If (s)he trivializes your concerns, get another doctor.

I wish all of you the very best.

Wow, this is all great advice. So many things to consider. thanks Sylvia

The SD is under all kinds of doctors care since the age of seven and we are aware of anxiety issues, bulimia and sociopathic tendencies (her therapists words) Frankly, all any of us ever do is talk about how to help her. Her mother would not allow us to put her on medication, but sent her to live with us. (unbelievable) Everyone is focused on this...She is not violent or perceivably malicious, but scary smart. YOu know, they say many successful CEOs are sociopaths... I predict she will be one of those.
I just see myself as the person who should focus on the needs and care of the other three children who are healthy and behaving. Someone needs to think of their best interests and protect us from future problems. Trust me, the SD is currently receiving all the care we can provide.

My husband and I did not have a will or any kind of legal document when he died except a POA. Everything was set up with right of survivor ship. When he died it was all mine, his kids and mine got nothing. There was nothing to be done except present his death certificate at the banks and courthouse to take his name off of everything. As soon as I could I made out my papers because when I die they would be needed. I did the POD and TOD, for my heirs and the POA, comfort care and living will. My attorney wrote out a bill of sale for the contents of the home for my heir. There will be no need for a will when the time comes. Except for the bill of sale, I made all the plans, my attorney just approved them and said it was perfect.

'Sociopathic tendencies' scares the liver out of me.

My mother was a sociopath, & she ruined numerous lives;
some of us are in denial, some of us are struggling and/or coping, some of us are dead (from natural causes, but I believe the stress & anxiety she dished out contributed to the health problems).

All mental illness scares me. I have 2 nieces that have been diagnosed as manic depressives or bi polar and one that should be. One says she is dangerous when she goes off her meds. I have a cousin in Arkansas who I befriended when others wouldn't and she turned on me. Told all the family that I stole something "off" her computer in the few minutes she was out of the room. She was going to call the police and have me arrested if I didn't give it back. My family new better and told her so.

Your SD is obviously suffering from mental illness and it looks like you are doing what is needed for her. Is it possible that all her parents have a united front for her well being?

Unless you are gravely ill I am wondering why you are having these thoughts. I would suggest that you and your husband seek a support group to help you deal with your SD issues.

Waiting until there's a plug to be pulled means you've waited too long.

& sometimes we start worrying about the less outrageous thing because the more outrageous thing is too scary or because people might think we were nuts if we admitted thinking about the more outrageous thing.

easier to worry about someone pulling the plug prematurely than to worry about someone dropping something in your coffee or cutting your brake lines.