Yeah, Crystal weapons were not the best I found. They may look the coolest, but there were better weapons before you reached the end.
Depends, the green quality weapons have random stats. Regardless, the NPC will in fact drop for inferior weapons. Case in point:
Crystal Bow - Speed Fast, DMG 151 dropped and replaced by:
Truth - Speed Fast, DMG 121
What is the speed / dmg / name of your current weapons?