Should I be handling Dad's finances? If so, how?

My dad is 65 and lives alone. He was diagnosed with Parkinson's four years ago and also had arthritis and chronic pain for about 5 years, so he's needed some help with the house and yard for some time now. But until this past summer he was mentally competent. Around that time, he became forgetful and once or twice, he confused what I think were dreams for reality. He also declined physically around the same time and started using a walker instead of a cane, sometimes needing a wheel chair, and still sometimes could barely get from room to room in the house.

I bought him a security pole so that he could get out of his chair, grab bars for the shower, and a few other handicapped accessories for the house. But recently he would sometimes fall or just not be able to get out of a chair, and called an ambulance a couple times, called me a couple times, and called a friend a couple times for help. At this point his only paid help was a cleaning lady who came once a week and an aid who came for a few hours on Fridays. I work full-time and can't pick up and leave work on a regular basis when he needs help.

These past couple months I've realized that he is not just forgetful or a little confused, he definitely has dementia (it is undiagnosed though). He has delusions and what are probably hallucinations.

My parents are divorced but my mom lives in the same town and worked in home health care for years. A few weeks ago she helped me arrange for aids to be at his house 24 hrs. After a week, my dad fired one of them, so since then he's had an aid about 16 hrs/day.

They are not charging a lot, but I had no idea what my dad could afford. I called him and asked if he could get some income statements and bills together so that we could do a budget. He told me that he had an old budget that was a couple years old and we could probably use that since not much had changed. I said that would be great and we could use that.

I went over to his house, and he picked up a kitchen towel and told me that was his budget. I said "No, that doesn't look like it...", and I looked around a bit but didn't see anything that looked like a budget form. He'd probably never had one, sometimes he confuses wishful thinking for reality.

He's always been an investor (and a really good one), but in the last year he's decided to sell his mutual funds and start trading stocks instead. Obviously, the age of 65 is NOT the time to get out of mutual funds and start playing with the stock market. He says he's up, but I can't be sure that's true. I'm just crossing my fingers, hoping and praying he won't loose his savings.

I have no POA, no legal rights. No idea of his financial situation. No idea how many accounts he has or where most of them are. I just recently got on top of my own finances and a written budget and detailed my future plans. It felt great, and it was a significant time investment. The thought of starting with absolutely zero background information and doing all of that for my dad, having NO idea where to start, is so overwhelming.

Dad recently visited the VA clinic to see if he could qualify for assistance and was assigned a case worker. I was hoping that maybe this person could be a resource to help me figure out what to do regarding his care and finances. I wasn't able to speak to her because she was on vacation, but the receptionist thought that was not part of what she does.

Also, Dad is not agreeable to me handling his financing. He really enjoys investing and likes having control. He would be extremely disappointed (and probably really angry) to have to stop.

He was so stable for years, all of this, needing care, legal matters, the fact that it is all downhill for here, everything seems so sudden and I was (still am) completely unprepared.