Thats why I used the disclaimer, "I think" and said that others would be more expert.
I understand.
In a mild steel, no amount of heat treatment will make a real difference. That's the kind of metal you probably have, and that's why it is smushing.
In a hardenable steel (say you borrowed metal from a junk leaf spring), you can heat it until cherry red (technically beyond the Curie point, when the metal is no longer attracted to a magnet), and then quench it (oil quench for higher carbon steels, water for lower, air for some alloys too; you really need to know what you're working with).
That will get you to a fully hardened (and brittle state).
Tempering requires heating tool steel until the surface turns a "straw" color (just past "champagne", and before "blue"). That will leave you in the toughest state. The "blue" line is too soft for a screwdriver tip (but is good for the shank). In that first page you linked, I would gently heat the screwdriver shank with an air-fuel torch (oxy-fuel is WAY too hot for tempering), and watch the blue line get to within 1/8" of the screwdriver tip.
In fact, I needed a hook to pull some seals from my car the other weekend, and rather than go out and buy a puller, I grabbed a junk screwdriver from the drawer, got out the torch, and made my own. With the proper hardening, it is now one of my favorite tools.
Once it hits a dull red, just about all of the hardening is gone in most steels (with the exception of things like HSS, but that's not really relevant here). That's way too far.
As for case hardening, this is fine to resist abrasion or sawing (like on a lock shackle), but not so great on a tool. I would expect that the hard surface will form micro cracks that will make the whole tool more likely to break.
What you need to do, is start with good steel. Let's see a picture of what you made, because I'm having a hard time picturing it. Then we can make some suggestions for what to use as a starting point. Machining it from billet seems awfully difficult.
