Some of this is simple.
Take a look at the diagram above. Trace along the power feed from the battery. With key off, is there a connection to any circuit?
Are any of those items on? For example is the door open? if the door is open the dome light circuit is complete. Close the door, or take the bulb out or the fuse out and its not.
With everything off, there should be no continuity to ground. Infinite resistance if you have a multimeter.
Additionally, read the ammeter!
If there are electrons moving in or out of the battery and through the ammeter, the needle will move. The more electrons flowing the more the needle deflects.
Full deflection in either direction indicates 40 amps and is a major problem. Disconnect the battery. Do not reconnect other than for trouble shooting as described above by 67Dart273. Or you can use the flasher unit as described in the Master Tech booklets and movies.
Correct.
It's possible the short was in the alternator.
Easy check. The output stud of the alternator should be isolated from the alternator housing. ie No continuity from stud to the housings (end shields). Shop manual has some other easy checks.
Easy one here.
Go to the diagram and place your finger on the feed to the turn signal flasher. Follow it back.
Q. Where does it take you?
A.____________
Next.
Follow it further back to the key switch.
Those fuses on the Q2 feed are switched 'Accessory'. Items on switched accessory only work with the key in run or accessory positions.
You can now make two categories.
Equipment/lights with power feeds that are always hot.
Equipment/lights with power feeds that are only hot through the key switch.