Why hot without neutral going downstream
It sounds like at one time this was a 240v circuit but it’s not now and you need a proper neutral.
Get some white or gray paint, or tape and coat both ends of the old cloth braid.
In the panel move the wire from the breaker to the ground buss (if a newer panel and the grounds and neutrals are separated to the white or grounded buss).
Then use the neutral at the receptacle. Break loose the neutral to ground jumper at the receptacle.
Connect the receptacle green screw to the box with a jumper wire or if self grounding receptacle the screw and box contact is all that is required.
These changes will make it much safer than using the conduit for a return path.