welcome to rock banging ... no, you are truly turned to flint, and there is no turning back ... to paraphrase the little green star wars fellow, "once rocks banged have you, forever will they dominate your range time..."
long ago and far away, I also tried to get the "sub" powders to go off in my flinter, and I had the same result as you did ... (funny how that works out...) that's the only downside of flint - you really have to have real black powder ... regrettably, this stuff is classed as an 'explosive' so the shipping and storage restrictions become a huge disincentive for retail sellers ... I try to make it a point to have plenty around, and i'll let others chime in on the best way to store BP ... (I just keep mine dry and cool, on a shelf ... pretty much the same conditions you'd use to store sugar, flour, or dry dog food)
goo luck and
Make Good Smoke! :grin: