By nuke blast, do you mean how big the nuke looks, or how much damage it deals out? If you want to edit the way it looks, just search for "FX_Nuke" in the FXList.ini and get the names of the particle systems it's using. Then, just edit those particle systems.
Quick question regarding cam default height. How do I make it so the camera starts at the regular height, and that's the default, except you can zoom out.