Iron toilet flange problem
Do you have any friends with a wire welder?  These little welders work well for filling the holes and retapping. 

I usually grind the heavy rust then mark well beyond the holes so I can re drill in the same place. 
Heat the area around the hole with a torch then using a wire welder Fill the holes with common wire let cool grind flat. Drill and tap then make sure to use brass screws so they don’t have problems. 

I have done this probably 2 dozen times with good success 3 or 4 on my own homes one that I know is still good 20 years ago. Several that we still owned for 10 years after and they were fine.

They make kits that you can cut the flange but if there is good metal and you can drop a weld it works better.