General

Just 30% it, don't think about it, just do it.

I'd just buy a pre-scrolled, prob cheaper in the end

Should I clean slate the failed slots or innocence scroll it if it has bad scrolling after im done.

CoGs or iCoGs are the way to go, got mine to 40 att.

I would go Shield atk 60, but those are both expensive and hard to find.

So COG/iCOG. Honesly, I chaosd mine (reg khanjar) back when there were no other chaos variations, and I got 8+19 so hey; normal chaoses may not be bad either.

shield for atk 10%/30% is the best though
icog is more convenient and better if you're lucky

CoGs or iCoGs yeah.