Welcome to the Forum. We have an 11 1/2 year-old male ruddy Abyssinian who was sporting the same blemishes as your Abyssinian is. These spots or blemishes first started to appear when Shadow was between 2 1/2 and 3 1/2 years old, and really haven't changed any since. I remember on numerous trips to the cattery seeing other ruddy Abbeys with the same condition in the breeding stock. I assume that this was a natural phenomenon from the way the breeder was talking about subtle color changes in the Abyssinian's coat over several years.
Shadow was just up on the desk here are a few moments ago, and I was able to compare the photos with his ears and the spots and textures matched. I also have a silver blue Abyssinian named Missy who is about 11 years old, and putting a flashlight under her ear it appears as if there is the same markings in her ears as well. Just not as many of them and not pronounced to the extent they are in the ruddy. I would have to think that these blemishes are caused from color pigmentations in the skin.
As far as warm ears go, our 2 Abyssinians seem to go through periods of hot and cool ears, and being like you, I assumed that possibly there was a fever, or problem. I have checked their temperatures from time to time when this has happened, and found the temperature to be normal.
After this being said, if you still feel a little bit uneasy over the situation I think I would be getting in contact with one of the Abyssinian clubs, or a breeder or 2, to get their feedback before going to the the vet again. This ear blemish could be a trait to the Abyssinian cats, and if the vet hasn't encountered this in the past he could be treating it blindly if he hasn't done research into it. Here's a website that has a list of clubs and breeders in it that might be of use to you.
If you do follow through on another course I would greatly appreciate hearing about the outcome.