scyther, evolve?

Wait for a nest. That one is hatched (I assume) so you'd need a bunch more candies to power it up if it gets a good set. I'd aim to farm more candies next time they nest near you OR try to catch a wild Level 30 one.

I would wait for a higher IV. I know he's rare but that means it will take longer to power up anyways. I have two of them and that's after carefully saving and maxing one and leaving one around 1600 for prestiging

You want it for Pokedex? Do it.
You may power it up? Wait till you find another one.
At the current Meta, Scizor has no use on both offense and defense, but it could change with the upcomming gym rework.

Depends on the Scyther's moveset. If it's good I'd leave it as is and evolve another hatch.