This is all new to me. Are there housing options for people on fixed income? I don't know where to start.

You can only help people who are willing to accept help. If they aren’t willing to receive help then you will be spinning your wheels and going nowhere. Not only that, you will experience even more frustration than you have now.

Maybe you parents like the isolation. AL means lots od people and staff trying to get them involved. The only good thing is, they have 3 good meals a day. Diabetes can disable but if Dad manages his, no need for a facility. As said they are allowed to live the way they want.

This may be hard for you to accept because it's your parents, but they have a right to live as they do.
If your father allows your mother's nonsense and histrionics to isolate him and not leave the house, that's on him not you.
My mother is much the same with the hypochondria, anxiety, and hysterics and has been so my entire life since I was a little kid.
All you can do is walk away.

There is such a thing as the "Right to Rot". This means that people (unless they've been deemed mentally incompetent) have a right to live any way they like. They can live in a mess, eat bad food, drink all day, or make themselves housebound. It's their choice. Also, pretty much everyone who cannot spend money endlessly without ever looking at a bank statement is on a "fixed" income.

If your parents own their own home, it can be sold and the proceeds used to get them into assisted living. There are AL decent AL facilities that will accept people who will have to go on Medicaid so long as they are able to cash pay for a certain amount of time. If they own property they will probably meet such requirements.
Do some research and find an AL facility who will work with them. After that it's up to them whether or not they go.

There may be VA help for your dad. You can call the VA or a third party (I used Patriot Angels) to file a claim for benefits.

As neither of your parents really suffer from dementia or other disabilities I do not think that they would qualify for Medicaid.

In terms of living today they are quite young, your parents. They are living their lives now today in much the same way they always have.
I would take care not to become too enmeshing with their lives. I would make certain they have access to the numbers to call on their own behalf with their own medical management teams. And I would extricate myself a bit. I might, in fact consider a move to another part of the country if at all an option.

This for now is about all I can advise you.
If you begin now, knowing their limitations, to enable helplessness your parents, they will quickly accept and descend into that helplessness.
This will mean DECADES of care needed as they can easily live another two decades.
If you become the caregiver you will sacrifice your own life to this.

I would suggest counseling for you. You now seem torn. You have witnessed their poor decision making and limitations for a lifetime and now you see aging added to the plate; you seem fearfully ready to take this all on. I would like you first to explore options.

I am really sorry about all your worries in this, and my heart goes out to you. It has to be a source of great anxiety to you.

You can’t “put” someone somewhere if they don’t want to go. How do your parents feel about such a move? Do they have assets to fund such a thing? You may be thinking prematurely about placing them.

How about suggesting to mom’s doctor that she needs treatment for anxiety, which could make a huge difference?

Of course you’re overwhelmed, but this is really not your problem to fix. If mom refuses help for her anxiety, I’d suggest you back off and not be so willing to sacrifice your life to make their life what you think is better. Then see what happens.

Why are you caring for them at all? Your mother and father don't want to do anything to help themselves. It's doubtful they'd willingly move into assisted living. Why would they, when they expect you to do it all for them?

You cannot help with your mom's mental illness. Next time she runs to the ER, meet with a social worker who can help her.

You cannot force your dad to eat how he should. He doesn't care about his health and all the pleading in the world won't make him care. It sounds like he's going to just eat himself to death.

It's sad to watch them slowly self-destruct, but you will self-destruct too if you take on their responsibilities. They have a legal right to make really bad decisions, unfortunately.

If you have a job, marriage, your own kids, whatever you have... do NOT sacrifice them for your parents. This site is full of people who quit jobs and uprooted their lives to "save" their parents. All that sacrifice did nothing but render them broken emotionally, physically, and financially.

They have the right to live how they want. You do not have to take care of them or rescue them. Just a reminder