First of all, I would like to add my thanks to you for this post. Sometimes I feel like I've been carrying for a while, but it has only been a matter of months. This is a great read. I just went and bought myself a new holster. It's for a 1911, but fits like a glove. I'll put more about that somewhere else...
Now, you ask abut the safety being off... Is your holster custom-made for a CZ? I think you said it was and posted pics, but I can't see pics at work. I have had this happen with the safety a couple of times, on a couple of different pistols. People who know more would probably say otherwise, but my feeling is that it may happen from time to time when you are wearing concealment holsters. In an offset drop holster, nothing is as likely to rub up against the side of the pistol, but in an IWB, it's right against your body, pants, or whatever all day. As long as the trigger is completely and securely covered, even if the safety comes off, you are not going to squeeze one off. But you might consider another holster, and see what happens.
Thanks again!