Sending you the biggest virtual hug! This absolutely is a life-altering dynamic, and one that nobody seems to talk about much. I wish I'd been more prepared for it when my mother died. It wasn't just losing her, it was losing the last person who has known me all of my life. It was becoming an orphan, and becoming "the older generation." All of that was incredibly destabilizing and upending. It's a real gift to others that you are talking so frankly about this. Lots of love to you, my friend...
Edit: I don’t know if this would be helpful for you, but I’m linking it just in case — not so much to do it the way I did, but just the process and the insights I gained about having a parent transition to becoming an ancestor. Hugs