Just noticed you already have the euthanesia planned for Monday:
“But then we have that hour or so where he’s a normal, happy cat and I don’t think I can go through with Monday’s euthanasia.”
Please do not go through with it, not just for the cat’s sake, but for yours. I think you would always regret it.
Try some anti-anxiety meds, as others and I suggested. Also, you say you are moving into an apartment, try to take the cat with you, they may allow it, knowing that it may only be for a few months — he may only have a few months or a year to live, let him be happy living with you and you will always be content that you made the difficult, but right decision.
We had a neurotic cat when I was in high school. The cat was down right destructive. My mother finally decided to take the cat to the SPCA and when she got about a mile from the house, the cat jumped out the window of the moving car. My mother thought, good, that’s over with and turned around and came home. Two weeks later the neurotic cat showed up back at the door, wanting to come in.
We had a neurotic cat when I was in high school. The cat was down right destructive. My mother finally decided to take the cat to the SPCA and when she got about a mile from the house, the cat jumped out the window of the moving car. My mother thought, good, that’s over with and turned around and came home. Two weeks later the neurotic cat showed up back at the door, wanting to come in.