That looks absolutely fine to me! Just bash off the handle with a hamer, wire wheel the steel and sharpen with a file. Is it a single bevel edge? or is it ground on both sides? By the looks of it it's a sngle bevel right handed hook, and you'll only need to shapren/grin d about 1cm of the edge. Everythign else but that will just be cosmetic. And cosmetic is personal preferance, not really a practical neccesity.
The angle grinder will remove all the rust, tarnishing and patina down to the bare steel leaving it shiny but I can't see any pitting tbh. I'd have to hold it to see for myself but it does look fine. Just crud on the surface.