Boy, it sure does sound like you're not getting fuel -- especially if it runs for a few seconds on the starting fluid, and once that's gone, it dies again.
Have you checked the fuel pressure regulator? I've never heard of one going bad on a Nissan, but I haven't been involved with Nissans very long either. It seems like that's the only fuel system component you HAVEN'T replaced yet.
There are also a myriad of things to check on the ignition side of things (like the oil in the distributor that rajnaz mentioned), but it sounds to me like the problem is in the fuel delivery.
