Modding ROF and Ammunition?

I've been looking at DoomIIIfiles.com for the longest time looking for the one mod I want and I've realized that I haven't been able to find one that fits exactly what I'm looking for.

So I was wondering if anyone could tell me how you up the rate of fire of each gun and alter the amount of ammunition it holds. As for power, I don't really care. Something else I'd like to know how to do is how to increase the radius of the flashlight's beam. Finally I'd also like to know how to slightly reduce the spread of the Chaingun and Shotgun's fire.

If anyone could tell me how I go about doing this, I'd be more appreciative.

~S1lent

For the weapon modding, take a look at the def files for each weapon. You can find them in the pak files with any unzipping tool.