I do understand what you are feeling. I can tell you, whether you go away or stay the feelings are the same. There is a helplessness that overcomes you because there is nothing you can do that will truly make a difference. It is what it is and we do not have the power to make it different.
Both of my parents have dementia. At this point they both recognize me but I know the time is coming when they may not, especially Mom. I made a very different decision. I actually moved them closer to me so I can have more one on one involvement in their care. But I am here to tell you that the sense of helplessness and loss is still there. I can pamper them and be there with them, but I can't do anything to even slow down what is happening to them.
Loss only hurts when we love what we are losing. It is the price of love. Yet the joy we receive from love far outweighs the pain of loss. A wise person once told me not to grieve for what I had lost but to celebrate the fact that I had it as long as I did. That advice has made a huge difference in the way I look at loss. Yes, it is better to have love and lose it than to never have it at all. I have amazing parents. Yes, they are now in the grips of a horrible disease that is slowly taking them from me. But the disease can never take away the amazing parents that I once had. That is what I hold on to and celebrate... that I did have them.
Right now I am not watching my parents die. They are living as best they can..... and I am doing the best that I can. I am not giving up my life to sit and watch them because that is not what they would want me to do. You did what you needed to do for you. Each of us makes our own decisions that are best for us at the moment we make them. There is no reason to look back with guilt or regret. You just go forward from this moment in the knowledge that you did the best you could in the moment. History is in the past and carved in stone, not to be changed. Tomorrow is just a promise for each of us. There is only today and what we do with it. Your father would not want you feeling as you do tonight.
Each of us is dying. There are no guarentees that you will live to see your father's death. So make the most of each day you have. Second guessing yourself is not making the most of each day you have. So celebrate life, that of your father and your own. Listen to what he would say to you if he was there. Life is for living