Stop playing with your tune, cas, etc. You are trying to retune your car to run on 5.5 cylinders, it's not going to happen.
Sounds like you have done a double wammie. Hard to start, rough idle, timing out, missing, harder to take off, etc all signs of a busted piston. Also your head gasket is stuffed, but this needs to be replaced when you rebuild the engine.
I know how you feel and recognize the symptoms, as i did the same thing on a race track, but mine didn't even blow any smoke. The only symptom i had, that made me realize something was wrong, was it was very hard to start on cold start. As soon as my mechanic heard the idle, when i pulled up to his w/shop, he knew straight away; "lost compression on one cylinder". My compression test, which i did myself, showed something like: 150, 149, 83, 151, 150, 152.
Here is a pic of my damage, that lead me to rebuild the engine; doesn't look like much, but halved the compression in that cylinder.
If you can't afford a proper rebuild, then just pull out your engine and buy another 2nd hand one. Problem is; you do not know what you're getting