Again, the next person who directly and pointedly responds to these questions instead of insulting me and claiming I lack mathematical acumen will be the very first.
Okay, here goes.
1. Proponents of this theory inevitably believe in the concept of a bashert and that God created a soul-mate for every person born. So how do they explain from a theological perspective how God could possibly be responsible for a demographic imbalance, as only He could be?
You’re making an incorrect assumption. I am a proponent of age gap but don’t believe every single person born has an inevitable soul-mate. That’s not what Chazal said, and even the gemara about the bas kol is explained by the meforshim as not necessarily applying in all situations.
Also, Chazal say shemoneh esreh l’chupah. Don’t blame G-d for a man made crisis caused by not following Chazal.
2. How is it moral and ethical for a shadchan to suggest anything other than the most suitable match for her client, and instead let a presumed demographic issue factor into her matchmaking?
Agreed. However, in the past, many boys would not have considered an otherwise suitable girl, simply because of age. That is b”H changing. Also, there are often equally suitable (to the shadchan’s eye) matches, so proposing one which would benefit society would not be unethical.
Also, proposing shidduchim to younger boys if they and their parents and rebbeim feel they are ready doesn’t involve this issue.
3. How is it moral and ethical for a shadchan to hide from singles that they are influenced by outside factors?
I’m not sure what you mean by that, but any broker (halachah views a shadchan as a type of broker) is influenced by factors that aren’t necessarily to the benefit of his clients, and has to know the halachos of what he must and what he need not disclose.
4. If it is true that women are at such a terrible disadvantage, why are women so quick to turn down suitors, often for the most trivial reasons? That is hardly the behavior one would expect from people who are supposedly competing for a mate from an endangered species. Did single women fail to get this memo?
Whether or not women turn down men for trivial reasons (men do the same, BTW) has nothing to do with the number disparity. They obviously don’t think their reasons are trivial, and would usually say they wouldn’t marry the guy if he was the last man on Earth. Anyway, he’s not.