Rough week for me as a caregiver

Well, I had a rough week taking care of dad. He is not wanting to cooperate when it comes to doing exercises, drinking fluids, etc, and just gets angry at me when I try to remind him of anything. But he is so forgetful – he has to have someone say it's time for meds or whatever – and I just had to decide to only remind about things ONE time, and if he doesn't want to participate in his care, then there is really no use letting him argue with me about it. He also was really rude to his physical therapist at the second session Friday, to the point where she had to talk with me about it off to the side. We had to go to a funeral earlier in the week for a very elderly relative, too, so I am sure thinking about mortality, losing independence, etc, adds up, but it is really hard to turn the other cheek or pretend it doesn't hurt when it feels intentionally rude.
Then after getting home from the miserable PT appt, I find my cat, who was DX with feline lymphoma cancer about 4 weeks ago, is not breathing right. The vet office is closing, and it sounds like she has forced exhalations, maybe fluid in the lungs from chest tumors, but who knows. Has not eaten well for a few days, but has eaten some. Mostly super pureed baby food meats, but I notice she isn't drinking much water anymore (had been on prednisone in addition to other chemo).
Hubby and I go out for some "us" time that evening, and when we come home the poor cat is even worse. She could walk and sat with us a few minutes on the couch, but fell out of my arms when I took her to her bed – she seemed really tired. I dreamt that night she has died, then woke early to take her to vet on Sat AM. She was laying oddly, with her legs out in every direction. Doesn't fuss to be laid in the carrier.
Once in waiting room, I wrapped her in a towel to keep her warm and try to comfort her, pet her, tell nice stories about her. DR isn't there yet so we are all just waiting. Some other folks talk with me, seeing how pathetic she is. They probably saw what I didn't; she was dying right there. She convulsed three times in a span of about 15 minutes, pawing rapidly and locking her arms straight out, panicked looking, unable to support her head. then breathing gradually stopped and her eyes glazed over, pupils enlarged. I couldn't believe it happened so abruptly. I took her to the exam room with an employee to check her heart, about the time DR came in to confirm.
At the time it happened so quickly, I didn't have time to process it al, but the rest of the day and today have been hard, remembering her throws of death, her sad meow, the lolling head, glazed eyes and even the tongue stuck out, the smell of elimination and death.
I realize this isn't a person, you all have seen worse, but I only hope I learned all this so I will handle the inevitable better down the road. I hope I can forget the bad days with dad, I can just feel compassion and sorrow and not feel like I am a source of resentment or whatever makes him so bitter. I feel like I am the scapegoat for him being mad he has cancer. He doesn't talk about feelings at all, he refuses, he doesn't need to, he just acts ugly to me. I wish so bad that bitterness would go away and we could have some more happy moments in this terrible part of life. It is really hard caring for someone who seems to reject you.