Rust! Should I sell it?

:rofl:
I appreciate the sense of humor, & wry "honesty", but I see it this way...FWIW..
1) If You're not a bodyman, & don't have the time & resources to learn, sell it if it's a model worth restoring.
2) If it's "just" a '69 Dart (non-GT/Swinger Slanty,273,318), the next owner may simply patch it up and make it a driver, and so can You.....if that works for You. Solid pop-rivet patches with most of the heavy rusted pieces cut out, & the rest treated, clean the undercoat off & lay fiberglass over the rough stuff after prepping. Make it fun to drive & enjoy. As long as the critical areas are solid or repaired proper, (torsion bar anchor member, frame rails/suspension mounting, front pillars, etc.), it can serve as a fun toy for years.
I have no idea what You paid, nor what Your expectations were, but this is where Your at....peace!