My suggestion would have been, and you can use it in the future if you get back to re-loading, would be to set up everything for a 300-400 rnd load session. Insure the press is well lit and have a 2nd person watch the entire activity and point out any possible issues as they occur. Because of your initial statement regarding how little the squib round went down the barrel (parts still in breech) I would guess this was a NO powder fail rather than an inaccurate charge fail.
I know you probably felt a bit overwhelmed with this whole process and the feedback you obtained here but unfortunately if you not actually there to see what is going on, your making educated guesses at the probable causes based on personal experience.
Now, to make matters worse, I will tell you that I know of at least 3 squibs from 9mm WWB in our club in the past year. So yes, even the factory can get it wrong sometimes.