I was under the impression most modern day stuff did indeed have that carbon content range. As for hardening I know most of the custom guys do that, maybe some off the rack gear today isn’t hardened but I haven’t found a nice harness in any of those shops yet. The whole Milan equipped 6000 soldiers thing I’ve heard off but 4000 of those were cavalry whom I assume wore at least a hardened breastplate. If not then the shock of a lance would get through it. Another thing is that those 4000 cavalrymen might just be the richest. If we take French nobility as an example then you are looking at the top 1-0.4% of the population. Wealth varied between nobles but they usually earned “a bit” more than your rank and file foot soldier. Another thing i’d like to bring up is that most so called munitions armor is from the 16th century and not the early 15th century, the second thing is that almost everything listed as munitions grade armor is quite evidently made for wear of footman and not cavalry (with the exception of some demi-lancers). Now I still need to look into the subject of swords more carefully but so far it appears the majority is heat treated which goes to show that the technique is doable (which is certainly probed by modern day blacksmiths).
Now if we take this into videogame realms then it would logically mean that munitions grade armor would be cheaper to buy and cheaper to maintain.
As for Tobias Capwell, well for one his armor has a nice black finish to it. Another factor would be that he doesn’t charge other cavalry with sharp lances, gets shot at with live ammunition, crossbow quarrels, gets stabbed by pikes, halberds and poleaxes, smacked by horseman’s and hammers/maces. Other things such as sieges and sleeping outdoors during a multiple day battle might also factor in.
You said hardness results in it being brittle which is exactly as I stated.
As for the rest that’s mostly true but he tested armor penetration with Joule required to penetrate and measured it at various angles.
As for penetration not correlating with damage what you mean?
Anyways this guy took an enormous amount of data from museum pieces (600) and even got permission to test on some antiques. What I said about the softer armor being a weakspot is something of an elementary truth which is backed by both modern science and common sense, why bother with hardening and tempering if a cold hammered piece of softer steel works the same?