Ubiquitin, no and no.
The numbers haven’t resolved themselves in the past, unless by a miracle. You still haven’t explained (and I don’t blame you, it’s impossible) how all girls can get married when there are more of them than boys (in shidduchim). Perforce, either your assumption that the numbers were always lopsided is incorrect, or your assumption that there were never a lot of older single girls is incorrect.
The analogy of musical chairs is indeed flawed, but conceptually it’s correct. The differences are: in musical chairs, when the music stops, all chairs are taken. In shidduchim, the music never really stops, and all chairs are not taken. This means that for the individual, there’s always hope. But on a broader level, you still can’t fit 112 bodies into 110 chairs.
Another difference is that although more chairs and players are constantly being added, there are more players being added than chairs, so the disparity becomes exacerbated, not improved (in numbers, not necessarily in percentages).
You also keep mixing cause and effect. If the numbers were even, boys would likely be less choosy. The reason they keep their “silly criteria” is because they can. The anecdotal evidence for this is compelling; we see time and again that boys who have “something against them” (overweight, dysfunctional family, BT, previous engagement or divorce, previous frumkeit struggles, etc.) are willing to, and do, “settle” for girls with similar “silly criteria”. Why? Simple – supply and demand. The same laws of supply and demand would reduce the requirements to consider (go out with) a girl, and would even out the dating.