'89 B2200--Tapping sound, dies in idle, loss of power

'89 Mazda B2200 (2.2 engine)
manual transmission
150866 miles

I started noticing a tapping sound, over a three day period it got worse-almost a knocking sound. The idle became really low so that when I stopped at a light or stop sign it would die. Then, the last time I drove it, I couldn't get up to highway speed, so I parked it.

All the plug wires have "fire" and the distributor has fire. When we unplug the 1 plug wire or the 2 plug wire, there's no change in the engine. When we unplug the 3 or 4 wire the engine dies. Also, the plugs at 1 and 2 are clean, while 3 & 4 are relatively dirty.

A friend suggested that it might be a rocker arm or rocker arm assembly.

Other symptoms that may be unrelated: overheating, oil leak, loss of coolant(don't know where it's going), some smoking, a/c and heater don't work.

If you can help me, know that I am illiterate when it comes to engine terminology--please be very specific and simplistic as possible.

Thank you
Andrea

P.S. I would love to make a donation to you guys if you can help me out, but I also want to let you know that I was just laid off. I'm a truck driver and the company I was working for is going out of business. So now I'm jobless and without transportation. If anyone can point me in the right direction, your help will be very appreciated.