My friend and i started making a Luigi's mansion themed map and we thought it would be a good idea if the players could started with a flamethrower. along with making the play start with a flame thrower we also wanted to change the amount of damage the flame thrower does, to make the beginning round slight more challenging.
       
        I want to know how to change starting weapon and make it weaker.

Okay do this to make the starting weapon weaker:

1. Goto root\raw\weapons\sp
2. find and copy m2_flamethrower_zombie (or your custom starting weapon if you have that)
3. Goto root\mods\MAPNAME\weapons\sp (if you dont have a weapons folder then create one with the sp folder of course)
4. paste the m2_flamethrower_zombie in the weapons folder
5. Edit the m2_flamethrower_zombie file with notepad++/sublime or something like that
6. Press ctrl+F and search for damage\30
7. change the "30" to any number you like. Lower numbers will make the gun weaker so like:
damage\15 to make it 2 times as weak
8. Check the m2_flamethrower_zombie file in the IWD file list at your mod builder and click on build mod
9. Enjoy! I hope I helped you