Hello Nick
If you want a metal hinge to last any length of time then you must make sure that the metal never yields. This means for the living hinge design that the flexure of the individual parts is small. You achieve this with thin material and fine strips.
Ordinary steel or aluminium will fail in this application. You need a spring steel or something like beryllium copper or some of the high nickel alloys such as Inconel X750. However, the latter two are very expensive, and beryllium dust is carcinogenic so I wouldn’t recommend laser cutting it.
Regarding the patent, it should get thrown out on prior art. Unfortunately, the US patent system rarely takes any notice of the fact that something has been in the public domain for centuries and just grants patents willy-nilly and lets the lawyers make small fortunes fighting it out in court.
Kind regards - John