Since the headlights will not light, you have a serious lack of voltage/current into the cars electrical system. Follow the battery cable to the solenoid and clean/replace any dirty/defective wires. The headlight draws power from a smaller wire that is connected under the positive cable connection at the starter solenoid, there is usually 3 wires besides the bat cable at the + side of the solenoid. 2 wires are about 14-16 gauge or smaller and 1 is a black with yellow tracer about 10 gauge wire. The blk/yel wire is the main power to the fuse panel, ignition switch and headlight switch, make sure it is good and has a clean connection. The other possibilty is a bad ground cable from the battery to the engine block.
I would start with the battery cables and then proceed to the smaller wires.
I would start with the battery cables and then proceed to the smaller wires.