I just want to mention something specifically about blunt weapons.
I really don't think the material of the blunt weapon should matter. A hammer or mace does not have an edge to hold. Damage should be based almost exclusively on the weight of the material and the strength and skill of the holder. Even the hardness of a material is practically irrelevant. A sufficiently sized block of soft lead attached to a wooden stick, for instance, will be impossible to break apart or damage significantly with handheld weapons. the same cannot be said about the shaft, but that is neither here nor there.
The same is also somewhat true with edged weapons that are large and heavy enough to deal blunt damage. A heavy, dull axe or a 2-handed sword that has been skillfully swung will have much more kinetic energy than a light, sharp axe or sword that was swung in a similar way. A scenario exists, for instance, where a heavy, dull bladed weapon would fail to penetrate armor but still inflict significantly more blunt force trauma than a light keen weapon of similar design that was swung with the same force and managed to penetrate the armor would do tissue damage via cutting. Material hardness and flexibility plays a much larger role in this situation, however, because while a hammerhead would be extremely unlikely to break in two, a sword is much thinner and more likely to be broken and even a bend or serious nick would seriously harm the weapon's ability to perform.
The only weapons where weight would either be irrelevant or detrimental would be piercing melee weapons. The weight of a spear does not factor into the amount of penetration nearly as much as in the previous examples, as spears and daggers rely on their keen edge, the ability of the point for liquid dynamics, and the raw strength of the user to achieve penetration.
As far as the change to bronze, well... bronze is categorically superior to iron in real life. As far as I know, iron was used primarily because iron was much more readily available than tin at that time.