1999 Chevy Lumina Engine knock, missing, stalling, surging

Wife's got a 99 lumina 3.1 liter with a rebuilt engine that has approx. 25,000 miles. Always seem to perform well with little maintenance and always kept fluids checked. Three days ago she states that all at once it started stalling, missing and making awful noise. This was about a mile from house. After a few stalls she made it home.

EXACTLY as described when I fired it up however, along with the bucking, missing and stalling comes an AWFUL noise. A TAPPING almost knocking sound that won't go away, sometimes it sounds as if the engine is binding up to the point that is stalls out.
I was hoping perhaps I might get lucky and the noise could be from misfires and fuel restriction. Changed fuel filter two days ago and cleaned throat with B-12. Same thing.
Seemed noise was coming from front of engine around idler pulley. Checked it and no problem with idler. In fact, took entire belt off and started again and noise is still prevalent with same miss and stalling present.
Disconnected front plug wires (wires closest to bumper) and they are firing strong. I'm in a wheelchair and the other wires below coils are rather tough for me to get to. Got to climb onto engine to pull a wire but too much trouble to get out, start engine and get back on top to pull another to check for fire. I don't really think that is causing the noise (from misfires) and it is certainly coming from engine.

I really kind of suspect a broken valve spring or something of that nature. Sound is not constant rythmic but rather irratic tapping getting louder at times and softer at others kind of like a valve has dropped and piston is hitting it. Missing bad at times as if I have a plug wire off.

Yesterday I ran a compression test. With throttle body butterfly open I get the following:
#2-195lbs, #4-180lbs, #6-140lbs,
#1-195lbs, #3-164lbs, #5-110lbs.
Not exactly sure what is normal, however, it seems rear of engine has lower comp. Than front cyls.

Today removed valve covers (pain in the#!) Yet did not see anything unusual. Spun over engine a few times. Minimal side to side movement on rocker arms. No signs of broken springs. Everything appears tight for whatever that is worth. I guess I will try and observe rocker arms in motion tommorow and perhaps determine if I do have a collapsed lifter.

With symptoms described and numbers above, does anyone have any thoughts, suggestions or ANYTHING that might shorten my suffering and aggravation with this hard to work on peice-0-vehicle?