You will not damage your sub frame by lifting it there, I've never seen a car rusted through the frame that bad. If you're talking about the rear pinch welds, I wouldn't worry about them. Even if the pinch is gone, the metal under it is what's really supporting the weight.
My uncle's 03 impala's brake line rusted and he had no brakes while doing 70 on the freeway. He was a mile from home and was able to pump them up enough to stop and get home but had it towed to a dealer that totally ripped him of for a brake line. Like $400 for one line from the ABS pump to the brake hose adapter on the LR side, it was insane. It's a good thing to inspect both the brake and fuel lines for excessive rust, and get them replaced if they're how you're describing it. It better to replace bad brake lines, even for a rather large amount, then to total your car. I've looked at mine after that pic was taken, they don't look too bad, but I should have checked the fuel lines too. I've seen a Buick something from 93 where the fuel line was dripping at least a drop a second, and they just keep driving it.