As a fundamental matter of thermodynamics, there really isn't a solution for energy within the paradigm Moebius established. The fundamental concept of "let people kill each other, then reincarnate them, then repeat, all while skimming a little life energy off the top to sustain ourselves" is a closed system out of which Moebius keeps siphoning energy, which means it will eventually run out because of the first law of thermodynamics. Whatever tricks are employed to improve the speed at which life energy can be harvested (as was happening in Omega or that colony where everyone is a first-termer), they're never going to be able to get out more energy than was involved in creating those lives in the first place. While it's never explicitly stated, I expect this is part of where the annihilation events come in: By turning large volumes of matter into energy, the deficit is fixed and the world can continue to function, though obviously this is still a finite solution.
That's kind of the thing though. It implies that reincarnating these people into new bodies isn't losing energy, it's gaining it somehow, completely flying in the face of thermodynamics. Like ultimately, they have all the energy and are just funneling it back into the system for what should be no gain, however, they do seem to be gaining.
Anyway, I'm still on chapter 6 so I'm not going to read further.