Engine needs 4 things to start and run: Compression, Air, Spark (at the right time), and the correct amount of fuel.
Compression: Because you are getting a sputter, you must have some compression. This is probably the last thing I would look at.
Air: Rarely is air the problem. Air is so easily available and there's very little that prevents air from getting into the engine. Will it start if you crack the throttle open a little bit (might indicate a problem with the IAC valve).
Spark at the right time: Are the spark plugs firing? If timing was 180 off, that would mean the spark plugs are firing at the top of the exhaust stroke rather than at the top of the compression stroke. I wouldn't expect even so much as a cough if the timing was that far off. The fact that the engine fires suggests to me that the timing is at least close.
Fuel: Other than replacing a few things, I don't see any mention of fuel system diagnosis. What is the fuel pressure? Spec is 60 psi, is it staying at 60 psi after the engine "starts?"
I've also found that it sometimes pays to ask the computer if it's seeing a problem. It doesn't always help, but, if you have access to a scanner/code reader, it only takes a few minutes to hook that up and see if the computer has any problems to report.