I suggest that the car be braced up, before any more sheet metal is removed!!! The repair is not a problem, sheet metal panels are available, and what is not available, should be easily made by a "Pro".

Keep posting pictures so that we can follow along

So what happened?! The car last summer was that red or orange one pictured and taken down it looked like those three rusty pics? Did that guy just start cutting without installing braces?! I have a shop in Arizona and it's amazing the amount of rust I am cutting out and replacing. The irony of that ! If you have any specific questions about rust and the removal, I'll do my best to answer them.