Progress pictures please 
That’s a lot of words for no pictures lol.
You can re sharpen your bits before spending more 
, even with that angle grinder if you don’t have a bench grinder/sander or bit sharpener. the key is to not let the tips/edges get so hot that they start to change color, and try to copy the same pitch. its worth a shot if the bit is already dead, and you might end up with one that tears through the metal quicker then it did new once you get your sharpening technique down.
I admire your resourcefulness, cant wait to see how it turns out.