I don't think it matters a whole lot what exactly the sequence of events was--I think you need to tear the motor down and inspect it carefully. If the Woodruff key sheared, the snout of the crank is probably trashed. And if the flywheel bolts backed, out, there's a good chance that end of the crank is hurting as well.
There's a good chance you'll need a new motor, quite frankly.
I hope I'm wrong!
--DD