ujm: I indeed don’t know the answer to the above questions. I was saying that these are indeed questions which must be explored.
Regarding the obligation of Pru Urvu that only men have, it is actually a machlokes, some arguing that women also have an obligation. Furthermore, the Igras Moshe writes that although each INDIVIDUAL woman doesn’t have an obligation to have children, there is a GENERAL obligation and ratzon hatorah for women in GENERAL to have children (I know this sounds like splitting hairs, but this is what he says). The Torah allowing men to marry multiple wives implies that the Torah prefers that women have a relatively easy time finding a shidduch (Rav Moshe explains that for this reason the Torah permits a sris b’yidei shamayim, so that there shouldn’t be a shidduch crisis by women).
Here are some quotes from secular sources regarding the age gap causing and resulting imbalance (again, this doesn’t necessarily imply that there is a crisis in the Orthodox community):
See, Women of Bangladesh: A Country Profile. United States, UN, 1995, p. 24 (“Bangladeshi women tend to marry men who are five to ten years senior in age, but on account of rapid population growth, the younger cohorts are substantially larger than the older ones resulting in a numerical shortage of eligible bridegrooms . . . parents have difficulties in finding husbands with suitable age gaps for their daughters. These problems have have resulted in delayed marriages and a reduction in the proportions getting married. Another important consequence of the favorable marriage market for men is an increase in divorce, separation and derivation”). See, also, Sautmann, Anja, Partner Search and Demographics: The Marriage Squeeze in India (August 23, 2011) (“When women marry younger than men, growing birth rates and a decline in child mortality lead to a surplus of women in the marriage market . . . to resolve the resulting surplus without women going unmarried, the age gap at marriage must decline”).