I'm not sure whether you're addressing me, Ladyalex, but if so...no I don't, I'm afraid. Certainly petermen (one word) were safe-crackers and so called from about 1900, but they got the name purely because safes were called peters by then, as I outlined earlier, and not for any connection with saltpetre.
Petre men (as two separate words), has existed in English since the 16th century, but - according to The Oxford English Dictionary (OED) - it meant only producers of saltpetre, not users and certainly not specifically for blowing safes.
One really can't just dismiss what the word-bible, the OED, has to say about word-origins and it says nothing at all about any connection between saltpetre and peter = safe. We can safely take it as read, therefore, that there is no such connection. Sorry!