No one really knows how lucky we were, I did read something the other day that said the whole situation was perfectly under control and I think that is a dangerous illusion. I guess the things we don't know are
1 How likely it was that a nuke could have been used.
2 The probability that a single nuke (or perhaps with a single response) could have been used without escalation towards a full scale exchange.
3 Especially given how long ago it is now and that (esp for USSR) ICBM's were in their infancy, how effective the weapons would have been.
I'm gonna go for 50/50, its the kind of odds I wouldn't bet anything significant that I value on, and yet there we were. Thank God it didn't happen.