My front tires (17" rim diameter) are 25" tall which are pretty short but are only a 45 aspect ratio. (Sidewall height is 45% of 225mm tire width) Generally as rim diameter increases, height of the tire sidewall decreases. (aspect ratio) The idea was to keep relatively the same tire diameter as wheel diameters grew over time.
I'm no tire expert but don't think you'll find a 45 aspect ratio tire in a 15" rim. (would be a rubber band...) A 60 aspect ratio would be more common but still be a pretty short tire. That's probably going to be about the shortest tire you can get on a 15" rim. BF Goodrich has some handy info on their site. https://www.bfgoodrichtires.com/tire/bf-goodrich/radial-t-a
I think you are on to something with the drop spindles. Would be interesting to see how low your fender opening is to the tire - especially once tire diameter is confirmed.
x4 on the anti-sway bar. The Addco bar was the cheapest one I found. I think it makes a huge difference in the way the car drives. My car is not an autocross or track car but does see spirited driving on the street. It was kind of a PITA to install however.
As for the KYB shocks. Decent considering how inexpensive they are but they're kind of harsh.