I owned a 944 with a distributor rotor that had been glued on by a previous owner. Not a bad idea but need to break it off to remove. Still, probably worthwhile.

If rotor loose, DME still fires at exact same time. What tells DME when to fire is speed/ref. sensor. Loose rotor doesn't affect those sensors one bit.

Spark will just jump across a different section of rotor... Towards one end or the other, then spark stops jumping when rotor is spun so far that spark tries to jump when it's not aimed at a plug-terminal. But spark timing is always same regardless of rotor position.

Now what happened in your case is probably built-up fuel due to misfires. Then it finally catches and extra fuel in exhaust ignites!