Dash lights

No, dash lights are a bit of a trick. The headlight switch has two power sources. One is not fused, feeds ONLY the headlights, and there is a breaker for that in/ on the switch

The tail/ park/ dash lamps are supplied by the fuse for the tail lamps. That power jumpers to the dash dimmer control, and the "dimmed" output goes TO the fuse box on TAN to the small INST fuse at one end of the box. Through the fuse, and then out to dimmer controlled lighting on orange.

So the tail lamps must be working, the dimmer must be "turned to left" and the INST fuse must be good.

Why do you say the rheostat is working?

First thing I'd do is monitor the INST fuse and diddle the rheostat, see if you have anything on either side of that fuse