Is this grill repair idea a bad one?

I would line the bottom of the grill with a couple layers of foil. then you can poke whatever holes in the vent places that you need for drafting the fire. I have actually done this when I needed more than the 2 large weber barrels we usually use. Old grills can be a problem.

Bad idea, don't

Bad idea. Get a grill at the thrift store.

I would be concerned with the toxins that might be released by the sealant or putty when heated. How about lining the bottom with heavy duty aluminum foil?

Don't seal up the holes, the fire will go out. Try using less coals so when you get done grilling there won't be so many left to burn up. You could try sticking wads of aluminum foil in the holes. Then if you need to take them out you can.

Putty is a bad idea, I'd bet a lot that it's toxic when it burns or melts.

You should not have charcoal left after grilling, all your charcoal should be glowing coals when you put your food on the grill and should be fine ash when you are done.

If you want to cover those holes, just use several layers of foil.

you need the holes on the bottom to open and close so you can control your fire intensity. air flow is key! you could maybe buy a replacement grill vent so it functions properly- if not just pitch it, its no good

yes

I think you need the holes to get a really hot fire. The amount of charcoal wasted is insignificant. Or you could extinguish the charcoal with a spray of water between grillings.

The holes in the bottom are the reason you got it for free. The steel is rotted and weak , The entire bottom will eventually fall out also what reaction will the putty have to fire. I consider it a safety hazard.