Count me in : ) If we assume that there are at least two not-completely-irrational agents, you are right. And in case there aren't, I don't think the scenario qualifies as a "game" theory. It's just a boring personal hell with 99 unconscious zombies. But given the negligible effect of punishment, I'd rather keep my dial at 30 just to keep the hope alive, than surrendering to the "policy".
So at month8 the edge grows 0.46 m/s. That doesn't sound very plausible to me.
In this timeline the area doubles about every week, so all the growth must happen in two dimensions (opposed to the corns weight gain), it couldn't get thicker. It means it's bandwidth for nutrient transport would not change, thus it couldn't support the exponential growth on the edges.
(although as between month2 and month3 it took a break of growth, some restructuring might have happened)
Only if we limit thinking to 1 round at a time. But thinking longer term: anyone changing to 30 (end being punished for it), immediately changed the landscape for everyone else: punishment reached it's maximum, from now on everyones' incentive is to lower theirs for immediate reward. And knowing that and thinking ahead at least two rounds, players are better off deviating, thus they would. Or at least they should.