Thank you for the suggestion! I tried to use TES5Edit to change the weapon damage and it worked perfectly. It turned out that there may be something wrong in the creation kit... Even after restarting my PC, mod edited by ck still cause CTD, and even worse, loading a mod edited by ck will cause ck to stop working as well... I got the ck from steam so I guess there might be something wrong with my ck setting... Anyway, thank you for recommending TES5edit! It works fine and it seems it could do everything ck can do...