Some of the problems can be alleviated if you don't assume that people stop working at 64. If people kept working at an older age, and that age kept increasing, the workforce size could stay stable, and possibly even grow.

The unmarried men problem is unsolvable barring a war. (And with the very very low death rates of wars these days, even that might not "help".)

Expect to see china legalize prostitution soon. They are almost not going to have a choice.

There is one other effect you will see. There is going to be intense competition for wives in china. Only the best will get one. Over time this natural selection should have very interesting implications for china.

I'm not sure what women in china look for (height? looks? brains?), (I'm not going to assume it's the same as in other countries). But whatever it is, these women will be shaping china's future.

One thing you should not expect is a dramatic change. It will be gradual, very very gradual. So I guess people will adjust.