94 Cadillac stalled on the highway. Wont start

U need a starting point.. Why not drain or oil and just put in its real capacity so u know where ur at with everything. Sounds like u may have blown gaskets somewhere?

Mentally understand your car by sections and dissect is what I would do. Oil from that system can leak from different sectors such as oil pan, rear main seal, rocker valve gasket, etc. When you park your car in the same exact spot each and every day the oil spot will tell you what's leaking. Oil pan under motor, rear main is behind the motor. Lay down cookie sheets under any vehicle to pinpoint the issue. Measure exactly where the sheets are in comparison to the components of the drive line. Section by section the oil will tattle on itself.

While your at it, check your fuel pump relay on fuse panel. For a car to just stop running while going down the road is awkward. Last resort check battery connections and cleanliness