Without more info it's hard to truly answer, but IMO, no. He has some use in arena at earlier stages, but he falls off pretty hard. The one thing he has going for him is that he's fairly decent in FW, but if you're asking, I expect it's because you're fairly early in the game, in which case there are probably better choices to level.

no

IMO, since he comes to you as an epic early in your game progression, I feel it is good to use him for practice. Until something better comes along.  I see so many try to make something good out of him but bottom line he does not really go the distance. But I would say yes, 5 star is ok if you want to try him out but not 6 star, I do not see that so often.  According to the ratings he is best in arena offense and defense.

Honestly, you should have given us more information.

People can make an agrument to level Jizoh to lvl 50.

People can make an agrument to not level Jizoh to lvl 50.