PCM Problem

So I've been having trouble since I bought the car in December. I have a 1998 Malibu with the 2.4L engine. I was originally having a misfire problem caused by a faulty coil cover. I changed the coil cover and spark plugs (ACDelco Plugs). I also had to replace the catilytic converter because the misfire was dumping fuel into the cat and stopped it up. Well I though this would solve all of my problems however my car still stutters at idle and occasionally during driving. It's so bad that it often causes the car to stall out or have serious trouble accelerating from a dead stop. I replaced the air filter, coils, and have checked all of my vaccum lines for leaks and nothing.

Two days ago my wife goes to crank the car and there are no interior lights and the dash lights don't come on when she turn the key to the on position. She tries to crank the car with no response and hears a clicking start inside the car somewhere. When she removes the key from the ignition, the clicking doesn't stop. I checked to see if it's the PCM/ECU that's doing the clicking and sure enough, I put my hand on the PCM and it's vibrating with the click, put my ear to it and it appears to be the source of the click, so I pull the plugs and it stops. I disconnect the battery and let the car sit for awhile and charge the battery (which had died). I plug the PCM up after 30 minutes and all the lights in the car come on and the dash lights up when we put the keys in, but as soon as my wife tries to crank the car, I hear a spark and the lights in the car and on the dash all die.

I'm about to purchase a new PCM. Is there anything else I should check that could have caused this problem before I try another PCM?