Need help, Dart won't start...

What you will see on coil+ with points closed will vary, I would say 6-9V depending on the type of coil, etc

With the points closed, move to the resistor and check it. One side of course will be same as coil, other should be very close to same as battery voltage

Have you read the MAD article? Have you wiring diagrams / shop manuals?

Your biggest suspects "IF" you can eliminate the ballast resistor, are the bulkhead connector, the switch connector, the ignition switch itself, and then bringing up the rear, if the headlights are also dim, is the ammeter connections, the fuse link and it's connections, and the harness welded splice