all fixed.
I ended up carefully drilling it out, large enough to fit the next biggest thread sized fitting (which it seems, is QUITE a bit larger)
then, I still didn't like the way it wasn't sitting quite flush, so I used the tube style metal fill putty (probably the same stuff HOT-ROD was talking about. I'd never seen that before, but it's AWESOME) ... waiting for it to fully cure (2 hours) now before I hit it again with the grease gun, but I'm sure it's going to be fine, until the next time I try to grind it off on a rock.