1993 Buick Riviera Car died then wouldn't start.

When I got it home I checked fuel pressure. It is at 45 PSI. When I checked for spark, it was missing or none found. I had the ignition module under the 3 coils check at a parts store. They said it tested ok. The engine is a 3.8 and talk to some people they said 3.8s have a tendency to have crank sensor and/or harmonic balancer issues. I replaced just the crank sensor and the car started just once. Then no spark again. Fuel pressure still at 45 PSI. Checked for faults found none found. It flashes only 12s. So I tried another crank sensor & new harmonic balancer. Still not starting. I tried another crank sensor brand because when I ohmed the different new brands one has only one reading left to right & right to left using a diode setting. Just like the one I removed at the start of the problem. I installed one that has 2 readings left to right & right to left using a diode setting. After the crank & harmonic parts, I got a 17 code number so I replaced the cam sensor. Now I am getting a 42 code fault. I tested the fuel pressure again & it is still at 45 PSI. Fuel cutoff relay circuit is one of 3 faults in the book. The other two are Electronic spark timing (EST) circuit - open or shorted to ground during engine run. The other is Direct ignition system (DIS) - bypass circuit open or shorted to ground during engine run. The engine is not running only cranking over to start. Does these two faults still apply. If so where to start & how do I test for opens or shorts. 04-17-2010 I unplugged the oxygen sensor by the fire wall center of the manifold. This is the only one I found. It did not allow the car to start. Another symptom the car is having is when the ignition is turned on, the dash powers up the LED dash, the rpm indicator is bouncing up & down like the engine is running or reviving. Other noises are coming from the engine compartment. It appears it is hunting for signals.