I have never seen a cat habitually curl its tail like this and he often curls it even tighter. Because he is so scared, I have never seen him with his tail straight up in the air.
A week later, he is coming when called and eats 2 meals a day most of the time. He also slept upstairs one night.
This morning, he was rolling around on his back in front of me, exposing his belly, a sign that he trusts me and I managed to scratch his head briefly. It was a good thing he allowed this because he had a piece of a cat's claw embedded in his forehead and I was able to remove it. He also has a tick on his cheek but I wasn't able to remove that, the fear kicked in and I got a slap so I let him be.
Unfortunately, relations with my cats have deteriorated because yet another cat has shown up, a large tuxedo male that visits and upsets my cats from time to time. I have never been able to catch this particular cat though.
So vet visit day for the small cat should happen very soon.