How far is to far gone?

IMO if there's rust perforation on a chassis structural member, the car is too far gone for me to bring back. Maybe the same opinion of rusty, bent structural members. People who are better equipped in skills, shop, and tools are able to work miracles.

If the car is important enough to you do what you can and farm the rest out to professionals. Realize that the decision to invest more in a car than it will ever be worth is an emotional decision, not a rational one. Good luck.