The priest says that St. John saw the number 666 in his vision, but it was actually 999 inverted. I'm not sure, but I don't believe St. John read modern Arabic numerals like we do. Didn't he read Roman numerals? I think if St. John saw the number 666, it would actually be DCLXVI.
The scene where Arnie is loading up at Stinger's HQ with all the weapons is very reminiscent of a similar scene in another Arnie movie, "Commando", with the pulling of buckles and tightening of belts etc.