The flashbacks remind me of many novels that reveal the important backstory through flashbacks in the first couple of chapters while everything is being put into place for the main story. I like them, they feel natural.
I also like the simple explanation for the gun weirdness: Monroe and his goons can't make new bullets. They don't say that it is impossible, just that Monroe can't do it. Doesn't really explain the swords though, but I'll live.