I don't own a 5th Gen Camaro, so anyone that has one, please correct me if you feel I'm wrong.... But here are my two cents:
With a manual and street tires, dumping the clutch at 5,000 RPM's will not do you any good. That's part of your problem right there. I can't tell you what RPM to launch at, but 5,000 is a lot. IMO- 2500 RPM's is a really good launch range, because that's where your cam is starting to make its power and you also have torque.
When you pull into the staging lanes, do not drive through the water box unless you're running full slicks. You cannot heat up street tires. The compound is completely different and will do you no good. All you'll be doing is wasting good street rubber. If you are running a DOT slick, once again, do not drive through the water box. Instead, drive around it and back into the water box. Why? You're front tires will pick the water up as well. When you're doing your burn out, your front tires are laying water down right where you're going to try and launch.
Also, you can over burn your slicks or DOT's if the burn out is too long. There is a point where you do more harm than good when you're doing a burn out. Get those tires too hot, and they become slick and ineffective.
Lastly, for reaction time, try leaving as soon as the 2nd amber light goes out and just before the third amber light comes on. If you wait till you see the last light, you waited too long.
Hope that helps!!!