A three wire/heated O2 seonsor will not hurt a thing. It only helps keep O2 sensor hot enough to stay Closed Loop Idle. It's also recommended as a cover up for overly rich idle that will cool a non heated O2 sensor and go Open Loop and run bad because fueling/spark is so far off.

No data log = NOT custom chip. Just another off the shelf chip we have seen many times before... every one I have seen had hardly any changes, some were just plain wrong. Although I already knew this when you told us about the playing with timing...

Sorry for the news. You are not the first nor will you be the last. But you are on the road to recovery and a good running engine! Whether you want to learn or hire a tuner (or both) to do this properly your at the right place.

Now do you have a cable to hook to a laptop and data log? You need data! How can you tune anything that you don't know is there?