Leggings provide the most free metal per smith/melt cycle (0.5 bars per iteration). I didn't get a chance to test high boots (my civ couldn't make them natively), but if they follow the same pattern as other armor, they should produce 0.2 bars per smithing, and 0.1 bars per melting (remember, you have to melt each one separately).
I must assume that this is a bug that will be fixed in some future version, who knows when. According to Quietust, the coins have been providing free metal since 23a, so it might be a while. (Free metal from leggings, battle axes, picks, gauntlets and other items is a new add-on to the bug.)
I'm not sure if this is true.
I had a very small amount of accessible candy in one of my forts. I knew about the bolt splitting and melting, but my archery range wasn't set up for bolt recovery. I checked the wiki and say that leggings give 150% bars when melted.
I made all of my candy into leggings and melted two of them down, expecting to get three bars. I'm not sure what the result of the melting was, but I remember I didn't have enough bars to make a single pair of leggings after the melting.
---truth---
Truth is difficult to define. Sure, what is true is what is 100% correct. However, a few hundred years ago, flight wasn't possible.Going about a certain speed was possible, but it turned your bones to mush. They were facts that were 100% correct
at the time. People didn't know better.
Speaking of which, did you know that modern science doesn't know how bees can fly? Yet, knowing (or not knowing) this, we've built spacecraft that can travel to other planets. That certainly says something about human ingenuity (or human stupidity, if you want to look at it that way) into perspective.