You don't need the anti run-on valve to make the light work, but you do need the third wire at the sender (which is a ground).
First thing I'd do is try grounding the wires at the sender. Dan's diagram shows the wire for the light as white with brown, but the colors may be hard to see or may not match the diagram; it won't hurt anything to temporarily just ground all 3 of them. If grounding the wires doesn't make the light come on, then you have an issue at the light, or maybe the brake warning lamp is burned out. The oil light is in series with the brake warning light, so if the brake warning is burned out or the PDWA switch is closed, the oil light doesn't work.
If grounding the wires does make the light come on, then I would double-check which wire goes to the light by grounding only it (or each wire in turn if you can't see the colors). Use a test light or ohmmeter/DMM to verify which pair of contacts are connected together on the pressure switch, then make sure the ground wire is on one of them and the wire to the light is on the other. If the light doesn't come on now, then either the ground wire or the switch is bad. (Even new parts sometimes don't work.)
If you do have to replace the switch again, get one of the earlier ones that only has one terminal. They're cheaper and more reliable than the 3 terminal ones; plus you can probably find one at the corner FLAPS. You'll have to leave the ARV disconnected obviously, but you weren't using it anyway.
PS, with all three wires at the sender grounded, the ARV will be energized as long as the ignition switch is off. Won't hurt anything at first, but don't leave it like that overnight or it will drain the battery.