Your RT's: Gett a practice tree. It can help you develop a reflex rythem even if you go through different motions. I footbrake but practice with a button. It translates to more consistent reactions at the track. But go for consistency rather than actual reaction time on the practice tree. (Unless you have an adjustable "rollout" and can get it close to what the car is doing.)

Car RT's: That's not easy. You may have to use shorter tires and other tricks to stiffen the suspension and frame.

60' time: I don't know enough about sticks to offer a lot of advice. But I know it's not easy. If you are not spinning or just a little, it can be "bogging" or just "flat". Don't know the rest of your combo, but I know of old 273 wagons with auto transmissions needing 5.13 to 5.57 gears to get their weight moving with a little engine. If you improve your 60'times with that weight, you'll have to watch for weak links in your drivetrain!