@annielou I have been following your post and it saddens me that you are in the exact same place that I am because this is no life.Mum died 8 years ago and she had already expressed concerns over dad's memory. I hadn't noticed but it soon became apparent that dad had a problem but nothing that could not be coped with.
Like you I started to help dad out with little things and spending time with him to try and keep him happy. We lunched 3 times a week and I would stay one night a week to watch TV with him. It was all very manageable to start with and I could still go to work and even have holidays but that changed two years ago when I had to stop dad from driving (long story) but it had to be done.
Dad was diagnosed alzheimers in 2017 and he has gone down fast since then. Shortly after this dad stopped eating and I had to do breakfast and dinner and shopping for him because he became to frail to go out. We continued like this for a while before we found out 18 months ago that dad could not eat because he has advanced oesophageal cancer so lots of appointments, stent fitted and dad could eat again so all well and good although he still had a terminal prognosis. So I carried on with the care the same as before but it was more difficult because dad could only eat certain foods safely. Anyway I left work at about this time because it had become impossible. The only help I got for a long time was from my husband who went on to have 3 heart attacks in 3 months so I was under a lot of stress at that time.
Dad had a hospital stay of 3 weeks back in March with pneumonia followed by a heart attack, 3 falls and a stroke but he recovered and came home. Now it is 24/7 care and like you I see my husband when he takes over for a night or 2 and I then get to see my son although he is very good too and will help me out if needed. I also get some help from my brother who was previously an invisible for a long time but it is not enough and can never be enough. You sound like you have taken on so much alone and it is impossible.
Dad will be 90 next year and we have been told that his cancer has stabilised so he could go on for another 5 years although that is unlikely to be honest but you never know.
What you are doing is unsustainable for any length of time. I spend my days and nights with a very pleasant and witty dad who does not know if it is 4 in the morning or 4 in the evening, he sleeps most of the day, thinks he is very fit when he is in danger of falling and likes to move nick nacks around. He cannot be left at night because he can't find the kitchen or bathroom, he can't even switch the TV on, he shaves 3 times a day, does not wash very well and I could go on and on like this.
I am lucky in that dad is compliant and still funny but this has worn me down and I don't know how my marriage has survived but it has somehow.
This will take it's toll on you if you let it, I don't know the answer but if you don't get help you will become like me, a prisoner in your parents home and that's what it is. I get day release every now and then and I know I should get out and enjoy myself but I don't, I just go home and hide in the house because that is how it has become for me. I am in my 3rd year of full time caring (meaning I got to go home at night) but 24/7 is a killer as far as I am concerned.
Get some help before you end up like me.