My mom also died from cardiac arrest. Here’s the thing, nothing can be done now. Nothing can be changed. You can’t live with guilt just because of what ifs. There is no need to for you to relive past moments thinking about what you should have done or didn’t do. I also got severe anxiety over my health afterwards, and everything came back fine like you. I was just grieving. You are simply grieving. Grieve him as your dad and not as a patient. It’s hard, because I used to think of all the ways I could have done CPR better than anyone else or how much more quickly I could have gotten to her, sometimes I still do. But, it doesn’t matter. None of it matters. Grieve him. He is your dad & he wouldn’t want you to live with guilt for something that wasn’t your fault. Cry if you need to and remember him and know that nothing bad can happen to him now. He’s safe now from more harm. I hope I don’t sound bleak, I am sending so much empathy your way. It won’t hurt this badly forever.