It sounds like you have "the farm cat disease", at least that's what we call it 'round hur' in I'awaThose respiratory infections in kittens are nasty. They are in no way easy to get rid of and take a lot of time to heal. I know both of our disease ridden farm rescued cats took at least a week on those antibiotics and eye drops before they got better. Both ended up getting a swollen shut eye from the infection.
I'm not sure if it's true, but I've been to several vets all a crossed Eastern Iowa and they all said the same thing. This RI found in kittens isn't really curable. It's treatable, but not curable, they have to grow out of it. Our first cat, Enzo, had horrible sneezes and his eye got watery/red every now and again for nearly a year. His eye bugs him rarely now, he's 3.5 years old now, but you can hardly tell, he just winks sometimes. Loony Luna, she's 2 years old now, and had it REALLY bad. She would get in sneezing fits that just wouldn't stop and that went on for over a year. She's much better now, hardly ever sneezes, but her eye does still water a little every once in awhile. It gets better with time! My mom also got a cat from a shelter who had it just as bad as my Luna, she is about the same age as Luna, and at the same healing stage. The shelter told my mom the same exact thing, they have meds to get through the infection, but they have to grow out of the rest.
Oh, I did have to get eye drops for Enzo one more time after the episode when we first got him as a kitten. I think that happened when he was about a year old. His eye was really inflamed and red.