Had to drag this up again, I went through something very much like this a week ago.
Same symptoms and everything.
Turns out it was the coil wires going into the coil that corroded off just enough to spark sometimes. (mainly when the plugs were out)
It would spark consistently and seem strong, but only kick and make a bit of smoke randomly.
Then once we replaced the coil with a brand new one, started first kick and then the smoke rolled out of the garage
Have to say there is a huge difference in spark intensity with a new coil.