Pontiac Repair: 1989 Pontiac Grand Prix no start, testing continuity, pontiac grand prix

Question
1989 Pontiac Grand Prix SE 2.8L V6/AT-loaded accessories.
I have a problem that this vehicle will not start. It will crank, with a new battery and  I have changed plugs and wires. I get spark on wires, fuel pump sounds like it is working to prime system when key is on and after cranking, get fuel pressure to rail when release/check valve on fuel rail is pressed. Car will run with "starting fluid" sprayed in intake, but runs very rough and seems muffled. Should I change the fuel filter again( only 3-4 months old)? It was running one day and next time I tried to start it, it only cranked. It was a very, very hot day last time run.
I had been advised at a muffler shop (new muffler installed) that the catalytic converter had broken ceramic plates inside, only a few days prior to no run condition.Could the converter being plugged be the cause of "no start"? Or is it possible it may be a relay(large type fuse under hood and wheel well) that is defective or even the Computer?
I have tested a few of the relays pertaining to the fuel and engine systems with a multi-tester by reading the schematics on the relay casing and testing continuity between contact points. I am not confident in this method of testing, if correct at all. Are relays testable or do I need to swap them out until or if these are found defective? I appreciate your help.

Answer
Yes you can test relays by using the schematic on the side of the relay.
Yes, it is very possible that the clogged converter is causing the no start condition.If the engine cant breathe, it cant run. Also, a converter will not go bad. There has to be some other problem that caused the converter to get too hot and break apart inside. The most common is a problem with the fuel mixture being too rich or too lean. Usually its an injector problem.
You said that it will run with starting fluid. That tells me that the ignition system is working, but you have a fuel system problem. Either you dont have any fuel pressure, or not enough, or the injectors are not working. These old 2.8 engines had alot of problems with shorted injectors. If you have more than a couple of shorted injectors, it can be enough to shut down the injector drivers in the computer.