There is also the fact that it wasn't officially sanctioned by the Federal government. At the time there weren't any laws that said it was legal to separate. So Quebec could vote all it wanted, but the feds could technically ignore it. The Fed's didn't stop it, or try to stop it, but they had said that the only thing it might do is cause the start of negotiations that may or may not lead to separation in the future.
With a mere one percent support for separation, the government could easily say that while it was regrettable, there was no legal way for Quebec to separate. If Quebec tried to go to the courts, a 1% majority would likely lead to a Federal win in the supreme court. The court would say that it needed a higher majority to separate, a clearer question, or that it was strictly illegal. So Quebec would at best have to do a revote.
If it was in the high 50's or 60's, there would be negotiations, probably with a focus on special distinction, a few more rights and things like that, but not actual separation.
In the 70's or higher the carving knives come out, and Quebec gets dismembered, leaving only a core region to separate. At that level people would realize that a friendly separation was probably best. But the government would have to negotiate hard to keep free passage on the St. Lawrence and other things, probably trading land for access.