I've going to give you the advice someone gave me. Unfortunately, I was a total mess and couldn't follow through on the advice, even though I wanted to! But here it is.
It seems pretty obvious that you do not want to be married any more. Don't worry about your daughter's marriage or your husband's medications right now. You have to think about yourself and what you are going to do and how you are going to do it.
First I recommend visiting your local public law library, or your public library, and figure out your rights, both as a married person and if you decide to go into divorce. I understand it's really scary right now, and a lot of that is because you lack a lot of information. Don't just go to the online forums. Figure out what your state's laws are. A librarian should be able to help, but even if not, keep looking.
Finances are a concern. Again, check your rights for alimony. Go to the community college and talk to a career counselor. Start going on job interviews. Who cares if it's for Starbucks
Get as independent as you possibly can. Prepare yourself and get yourself in a position of advantage. You probably don't want to hurt your husband, but it sounds like you need to get away. Is there someone you can visit? Someone you can call? You're not sleeping in the same bed as your husband; are you sleeping in the same room? Can you make a room of the house into your own?
Consider all the possibilities. Get your ducks in a row. When you feel calm and ready to ACT on your decision, talk to your husband and tell him you have MADE your decision. The details are just details-- they come after the decision. It sounds like you have already decided.
I didn't get this advice early enough, and I practically ran out of the house in the middle of the night, I just couldn't stand being with my husband for one more minute! In retrospect, it seems a little dramatic, but I was completely overwhelmed and stressed and unhappy. It's really hard when you feel like you're about to explode; I felt the same. I hope you can keep from blowing up, unlike me
Sorry for the length, I hope I've helped.