What you're missing is simple math. TDC is at the halfway point between where the piston meets the stop rotating one way and then the other. That's "the only place" it is. TDC is the basis for every single operation of that engine. It is the root of every single camshaft and valve event. It is essential to know EXACTLY where it is and that it's RIGHT, not "guessed with a screwdriver". That's why I'm hammering on it. It doesn't seem to be getting through. Unless that one thing is verified 100%, every single "other thing" could be wrong.
If this was my car and I was in your shoes, I would be doing everything people were suggesting........ESPECIALLY since it's FREE! I'll leave you with it this time. I've tried, beat it to death and done all I can. It's the one thing you haven't done, yet it STILL won't run.
If you ever do check it, I hope it's right. I hope it's something simple like the MSD box or some such, but you had a MECHANICAL FAILURE. TDC would have been then FIRST thing on my list to verify, absolutely, 100%.
Good luck!