I replaced my brass lugs with stainless steel bolts, so no 8astard can pull the grill off. If it was me I'd do this:-
Take the brass lugs out and clean up the crap around the thread that's left. Make good with JB Weld.
For those positions where the thread has disappeared, you could either JB Weld a threaded collar into the void or thread the JB weld.
Use stainless nuts and bolts instead of the brass lugs and you should be ok - I mean it's not like you are bolting together the Tyne bridge.
I too have brass lugs lying around - ... and eye nose where dey are