Do you feel like the stress of caring for your parent brings back past traumas they created?

You can oversee but you don't have to be involved anymore than you need to be. If he eventually needs care you will not provide, then u can place him or turn his care over to the State. You have choices. You can set boundries.

100% Daily, sometimes hourly. Sometimes I can't sit in the room with my mother because of it.

Absolutely!

I was severely abused by my OB (who died about 10 years ago) and it really did a number on my sense of self worth.

Mother WAS aware of it, but blamed me, in some weird convoluted way, for it. (what 3 yo has the capability of 'making' and older sibling sexually abuse them??)

She blamed me, of course, since OB was perfection on a plate.

I did not realize and fully comprehend the number that this abuse did on my until I crashed and burned in my 40's and tons of therapy brought back the monster. I re-lived all the yuck through EMDR, and while it was horrible to re-experience the abuse, I was able to compartmentalize and move forward. Turns out, OB had also molested my YB and YS. And a lot of kids in the neighborhood AND his own kids.

To this day my mom blames me. Nothing is going to alter that paradigm. I have quit trying.

Trying to be her advocate and helping to care for her really, ramped up my anxiety, and I finally had to step out and away.

I have 4 living sibs and one has primary care of mom. He's going to get her entire inheritance, but he doesn't know it.

If I were in your shoes--being alone, I would put up some mighty big walls and be as in control of what kinds of things you will and won't do for dad.

A therapist is, IMHO, a friend you PAY. I can say ANYTHING to mine and she always helps. I'm 66 and still grieving, to an extent, the lack of self worth that I was 'given'.

And my sibs are no help whatsoever. So, don't think that just b/c you have sibs somehow it's better. It can be worse.

I would suggest therapy. For myself I would not care for an abusive person, whether parent or not. That's just me, but I was lucky in my parents, and when we have suffered abuse it can form us to "serve".
I would contact a Licensed Social Worker in private practice to comb out what you want to do. You have accepted POA. You need to come to the conclusion in your own mind that what you have chosen is the best you can do out of a bad situation, OR find a way to untangle from Dad. Many folks have not had children. There is no one to take on their affairs other than the state and a court appointed Fiduciary. There is a way that doesn't include you.
So really, this is a matter of making your choice and being AT PEACE with it. You aren't alone and there is help out there for you. I wish you the best.

I totally understand how you feel. I, too, am an only child, my father's only relative, and we never had a good relationship. After over 70 years of being guilted into doing whatever he wanted I finally have established boundaries of what I am willing to do for him and what I am not. Luckily he lives in assisted living where I know his basic needs are met. I no longer live in the local area but I visit every three weeks to keep some connection to him and to check on things. I have a calendar schedule to call him every few days and I keep the calls short. It helps to have a schedule, much like you'd have for a job. That way I don't think about him between the pre-scheduled activities and I have more of my life back. I no longer listen to people who tell me "you're so lucky to still have your dad" or "It's a blessing he's still alive," No, I'm not lucky and he's lived 101 years, most of it being angry.

My suggestion is to make a list of the things you need to get done for him, and what needs to be done on a routine basis (paying bills, banking, etc) and set it up on a schedule. Try to set up his care so that you don't need to deal with things on a daily basis, just devote one day every week or two or three to him. Realize that no matter what you do he will be angry and abusive and it is not your fault or your problem to solve. Forgive yourself and don't accept the guilt. And when people tell you how lucky you are just stay silent because they have no idea what they are talking about.

If your part of the sea does not contain enough relatives, due to any reason (smaller family, moved away or even non-helpers) - could you consider casting your net wider? Eg to include non-family?

Then you could concentrate more on being his Advocate & less on his daily 'stuff'.

How often do you have to help now? What tasks do you do that you would rather not?