Short on Circuit 7 (not six) - 1974 Plymouth Valiant Scamp

Is it possible you mean circuit #7? In your photo, you have fuse 7 empty. Fuse #6 in that photo is the first one top left, and is fused for 3 amps.

The items you mentioned... trunk light, buzzer, E-Flashers... are non-switched items. The items Townsend quoted you from the book are all switch fed. Plus, you said you drove the car. If the run ignition run circuit in included for fuse 6, seems that fuse 6 would need to be in good order for the engine to run.
You are correct. I was mistaken. It's circuit 7 that's been the issue. I'll edit that post. Thank you!