How many demons (as opposed to Fallen) do or do not have Hellfire is speculation. Even if
none of them do, however, RAW claims that all Fallen do, and WoJ supports that. So
if you go with the Pope's assessment on the Fallen population (and I'd argue he is more an expert than any of us on this forum), then that's more than 133 million sources of Hellfire. That's a lot of Hellfire -- and also a lot of speculation, though based on studies made by the best experts in the field I could find.
Of those Fallen, we know that in DF 30 of them closed escrow on coinfront real estate, and RAW/WoJ indicates that all of them have access to Hellfire. Of those 30, only several are
known to have granted Hellfire to their human counterparts, as recorded in the novels and DFRPG. That list includes Thorned Namshiel, Saluriel/Quintus, and Lash/Harry. One third of those (Lash/Harry) are
not considered affiliated with the Order of the Blackened Denarius. It might also be worth noting that in the case of Lash/Harry, Hellfire was being granted not by a Fallen, but by the mental shadow of a Fallen.
Bottom line, I still disagree with your sweeping statistics, based on a sampling of about 0.00000225% of the Fallen with only 67% success rate.