The technique was called "killing intent in a physical form" yet it couldn't kill Mahoraga directly as the name would suggest. Don't take everything too literally
No, the cursed spirit equivalent for the simurians are docile and benevolent hence why they were revolted when they saw humans killing curses not understanding that curses are formed via negative emotions.
Also the “killing intent in physical form” can also be translated as “mass with killing intent” and when you examine it all it means is that he can give his light mass (hence why there are persistent glow sticks).
Dabura can probably make light shields, light sabers, and what not.