help please - lost power to cigar lighter , dome light , map light and more 1972 dart

The fusible link protects everything from a battery short.
If there is voltage at the fuse box, then the fusible link is intact.
- That said, if there is just one strand remaining, it will still show battery voltage when everything is off.
Same with a poor connection anywhere. The connection only reveals itself to have high resistance when current is trying to flow through it.

Operationally the wiring on your '72 will look something like this.
The shop manual diagram will have the details of the layout, colors, connectors, etc. Look to see what the cigar lighter and dome light share on the fuse panel.
They probably use the same feed wire from the main junction.

Main_charging_wires_pluss.png