ECU swap

At some point you have to realize the least expensive and fastest way to get this solved is by taking it to a mechanic; that is unless you're doing it for the challenge. The most expensive way to diagnose something like this is by throwing random parts at it. Each time you replace a sensor, the computer has to relearn its characteristic since no two sensors are ever exactly alike. There is a specific set of conditions that must occur for the computer to compare one new sensor's readings with other things it knows from other sensors. When you replace a second or third part that are used to learn the characteristics of the first one, the computer gets confused and there's no way the engine is going to run right, even if you accidentally replace the original defective part.

Have you even determined if the fuel pump is running and if you have fuel pressure? We know you have spark since it runs on starting fluid. As for a used computer, it may be able to be reflashed with updated software but it should not need to be programmed to your specific car at the dealership. GM didn't start that nonsense until 2002.