You said that
At the fuel rail it sounded like air was being pumped in. 5) I pulled the feed hose from the pump and got a good, strong flow of fuel from it.
Would you have inverted fuel lines (feeding/return line), if you hear air like sound in fuel rail while jumping fuel relay? Maybe also clogged fuel filter/fuel line between pump and manifold?
Concerning the suggestion of CPS, if you have spark while cranking it seem your CPS works fine.
It is possible the fuel pressure regulator is faulty, like if its internal valve is stuck closed, no fuel goes in manifold.
Might be worth to see if you have fuel coming out after the FPR or pressure test it.
1993 (build 93/05) 525i automatic M50TU (vanos) 263K miles (ca. 423000 km) in Montreal, Canada (bought the car 9 years ago in San Diego, CA)