The ring is set in the plaster.
I have never seen one so far off center. It was probably fine with the original cover, but the adapter (black plate on your cover) must mostly cover it, even installed off center itself.
As a professional with liability and compliance concerns I would be referring you to a plaster guy to replace the ring and put in a compliant sump. Not a bad idea, but a little pricey and good plasterers can be booked months out.
As some guy on a pool forum, I would say drill it out at the two oval holes in the ring, set plastic anchors (a HUGE no-no as a contractor) with a sealant to prevent seeping, cut out a section of the adapter plate to allow some flow if needed, and attach it with SS screws.
I have no idea what to do about the bump in the plaster, as I don't do plaster. Maybe you could trim the adapter plate and sand down the cover in that spot to get a flush fit.
The rust is not the ring "anchors", as they are just brass nuts set in the plastic ring, or maybe just holes in some plastic. It is the screws used to attach the adapter plate, which were probably not stainless steel. You can drill those out if you choose, or put a silicone band-aid on them to get you by for a few years. I doubt they will be much of an issue anyway.