Is bronze's new tin cost intended? It makes it much much more difficult to distribute enough to bronze a kingdom, and impossible to field a large bronze army/fleet.
I think a decrease in tin needed in smelters back to 1 and a decrease in tin production in the mines would be good.
This way you can still distribute bronze in your kingdom by shipping tin and smelting it at the settlement where it arrives while at the same time tin is still more valuable than copper.