Regarding weapon range: There is a range value in the tech files, so yes, it can be changed to anything, you just have to mind the researches which alter that value.
I've personally tested the effects of ridiculous range and find that the game adds some pretty big errors to shots longer than 10. Heck, the Thor's Hammer should give you a good hint, seeing how it's often enough missing its target, the middle of its target tile.