Kefa

He's forgetting about the independent action skill of the archer class which allows them to stay alive without a master for a few days.

Wasn't it stated that he actually didn't love her in the heaven's feel route and that he cried for another reason?

Aren't magicians the ones who use true magic? The ones who use normal magecraft are magus(magi for plural).

Nietzsche?

Their kekkei genkai slowly kills them and makes them more aggressive, not sure if I remember right, but the more talented clansmen die quicker.

Did you fail?

He didn't create it, infinity is the cursed technique of the gojo clan, but to fully master six eyes are required.

The perks are part of slayer class.

Kaguya has All-killing ash bones