I don't have time to go over this tonight, but here's a tip. Smell the exhaust. Unburnt fuel causes a lean reading on a wideband. You are fighting with this more than someone with experience but no more than any other novice, especially when they've made too many changes at the same time. Set the fuel pressure to stock. Set the NEO to zero across the board. Look to see how far rich or low you are across the board and make a mainscale adjustment to account for that. Then trim each section as needed on an individual basis. The ECU doesn't learn how the engine is running from one single session and I believe it continually adjusts to changes as well. After the first couple drives it should be pretty well set though. Resetting the ECU when the car is cold or hot isn't going to do much it's looking at averages from multiple samples.
DON'T PANIC
A lean idle isn't an engine killer unless other things are wrong (no EGR to cool things down, heavily advance ignition, etc.).
Is the stock O2 sensor still installed? Or is the AEM providing the ECU with a narrowband signal? If the AEM is providing the signal make sure it's properly scaled and the wiring is rock solid... Doesn't take much to throw the signal off enough to cause the ECU to think the AFR is WAY off and perpetually over correct.