Classic/Antique Car Repair: 1981 pontiac bonneville 3.8, pontiac bonneville, valve lifter

Question
Yesterday my car was running. Yes the oil light came on when you came to a stop but the oil was full. I went on a long trip approx 25 miles and when I got where I was going I shut the car off for approx an hour. when I went to leave the car seemed to have on power or compression and was backfiring continually, not out of the tail pipe but from the carberator. I had no power whatsoever when trying to go up a hill, had to keep the pedal maxed just to inch up, had to push a few times... ended up getting a tow home. today I changed the plugs, and wires, and distributor and rotor. all had damage, every plug was fouled with soot like carbon not oil or gas but still bad, the distributor and rotor had burn spots and damage and the distributor was extremely dirty inside. the wires were old and melted or broken in places. I set the engine to top dead center and made sure my plugs were wired correctly by the 165432, The car starts but has a popping like sound coming from the carb. it is pretty steady and when you gas it with the breather off it shoots gas up each time it makes the sound. I am at a loss. I even moved the timing up a bit to try to help it. I have read many things to try... a burnt valve? the cam? change timing chain? what would you suggest be the next step in discovering the problem. should I just start a tear down of the engine and go till I find a problem? I have a friend helping me and he has spent alot of time on this. This car was a gift to me when my honda accord threw a rod. Being a single mom of 4 I really need a car and any and all input would be greatly appreciated... Thank you.

Answer
The first thing that I would do now is to get a compression check on the engine. That will tell you if the valves are burned or ok. The fact that the oil pressure light was coming on at idle leads me to believe that there is an internal problem in the engine, perhaps in a valve lifter, rocker arm, or push rod that is not activating a valve and allowing oil to flow out reducing pressure. But I would compression check the engine before buying another part and then let me know what the compression readings are if you want move help.
Brad