This is an excellent point, the material these components are made out of aren't designed to melt. Thinking of them like you would think of the macro level circuitry we work with doesn't really make any sense. Again, this point is spot on. The efuse isn't burned, it has its resistance increase through electromigration. Probably not. Anything you would do to bypass the eFuses would almost certainly destroy the rest of the IC. Possibly, but a lot of these exploits are due to design flaws in the IC. Modern chips tend to have much better eFuse design, where it may be possible to bypass, but it is becoming less likely. Another thing that is important to remember is that many computer components are actually orders of magnitude smaller than this, and they all work just fine (plus or minus some weird quantum effects that screw things up sometimes). When things get this small, a lot of the stuff that makes sense at the macro level falls apart.