Low beam doesn't work. High beam will work, but cuts off and then on again. Also, if related, the switch must be jiggled for the interior dash lights to work. Could all of the problem be in the switch?
It's most likely two separate circuits, and two separate issues. Your interior lights, as you pointed out, work when you jiggle the switch. So, if you pull the switch out, and connect the wires directly, does the interior light stay on constant? If so, it's the switch.
As for the headlights: Stupid, obvious, obligatory question: You've tried replacing the bulbs? One of the filaments can completely burn out, leaving the high beams to work fine. And maybe that filament is making a partial connection occasionally.
More likely, you've got a power lead with a poor connection, possibly even at the head light fixture (hopefully there, since anything else is going to require a bit of detective work on the wiring harness.)