Main thing is to first remove the broken off screw.
Have you tried an EasyOut or Grab It?
Having said that and looking at the carnage I would not suggest the OP attempt to fix anything with power tools or taps, it could make things worse.
To clean up the holes there are
clean out taps (thread restorers) that you screw in by hand that remove gunk but won't cut new threads
@landingtheLC : if new screws will go into those threads ie: a test fit before you install a new pump cover you won't need to use a tap or thread restorer. I would just blow them out with brake cleaner
(cover your eyes and/or look away as the cleaner will blow straight back at your face!!)
The critical suface is the flat area where the oil pump cover clamps down onto the corresponding mating surface of the timing cover, but that doesn't look that bad and FIPG may be work well along with the O-ring IMHO
As mentioned above JB Weld could work but IME for that area it might be hard to keep it in place ie: the JB Weld will want to slump or slide downward. That could be fixed later with a dremel if too much got into the gland for the O-ring but again, difficult to work in that area for anyone and too easy to damage the soft aluminum.
So I would not suggest using a dremel.
@landingtheLC :
a safer option might be to use FIPG (form in place gasket) to fill the damaged areas after everything is completely degreased with brake cleaner for example
Technically, nothing should get into the gland or interfere with the movement of the O-ring but FWIW I've used
a very small line of FIPG placed on the outer rim of the face of the oil pump cover just before installing the cover.
One tip: to help get the cover on evenly once the FIPG has been applied, I've taken longer screws of the same thread and cut the heads off (made my own studs) then threaded a couple of those into a couple of holes. That allows you to "hang" the cover first then slide it back into place without the cover sliding/slipping around and disturbing the FIPG, if that makes sense, then start installing the screws and remove the studs. Let that cure for at least a few hours (better overnight) before you start the vehicle.