Very rough idle, sulfur smell from exhaust

I have a '98 ZX2 with 170,000 miles. Suddenly started running rough at idle and stalling (smooth at highway speeds). I tuned it up (wires, plugs, fuel, air filters, and PCV valve. #3 ignition coil tested bad (put a timing light on that wire, intermittent flash, but had it on the other 3 wires). Replaced the coil. No change. It idles so rough that it stalls and shakes the whole car. The exhaust smells heavily like sulfur when you rev it up, and if I out my hand over the exhaust, it stalls if I block it for a few seconds....does this sound like a bad catalytic converter ?? What should I look for next ???

Did some checking today on the ZX2. When I turn the key on and check for pressure at the test valve on the fuel rail, the pressure is nearly non-existant unless it's running. I am thinking fuel injector(s). The Zetec engine does not have a fuel pressure regulator, just a fuel pressure sensor. My wife has a habit of driving with the fuel tank very low, maybe one of the injectors is stuck open ??