king of no killing, does it mean that he cant be killed?! pls excuse my lame brain --"

Means he'll die if he killed someone directly.

As long as Dokja doesn't kill anyone, if he dies, he can come back a certain number of times. Once he kills someone directly, he loses that skill and is once again vulnerable to death.

No he won't die, he will lose the privilege. The skill means that you can resurrect if you saved 100 ppl or helped them each time.