Replace the door switches before you go chasing a bunch of gremlins. The thing about electrical bugs is if you have reason to suspect one component it's a complete waste of time to look elsewhere. They ought to call it an electrical octopus since a single bad component has tentacles that reach out to glitch anything sharing power or ground.
Bare wires have probably oxidized from exposure and could be hiding broken conductor strands. Wires and switches are just mechanical components, the problem comes when people view them thru a cloud of mystery because they're electrical. The harder something is to access, the more likely it's to blame
One other thing...without a headliner many GM dome lights will short to the roof.
These old headlight switches have decades of carrying the headlight's current. If you can't afford/find a new one, pull it out and hose it with electrical parts cleaner while working the mechanism about a hundred times. Both rotation and pull. Allow to dry. When you reinstall, add a pair of relays up front to take the headlight's load off the switch. Car's lighting and electrical performance will jump significantly as the headlight load is removed from the wire which supplies interior power.