Unfortunately we're looking at 20+ turns for Gunpowder as our reasonable pace, even counting for growth. This is due to our fairly large unit support cost (which I did nothing to bring down--stuff happens). Next player should resume full time settlers from Leipzig to fill the Dutch lands for unit support, and try to devote some towns to aqueducts (to get to size 7).
And I don't want to count on saltpeter, even if it seems like we "should" have some. What I'd like to ideally see is for us to get the situation fully under control in the south, and use longbows the horse army (not the spear army, which will be needed elsewhere) to hold a well-defined chokepoint there. Use the spear army, the longbow army (right now do not fill with more than 1 longbow) and a bunch of horses + longbows to assault Greece or Persia. Persia seems to have most of the iron; not sure if Greece does, they've been sending hoplites plus horses. If Greece has no iron, I'm afraid that I have to say that going for Persia instead is vital. We can't wait another 50-60 turns to get a real assault going.