[Wauthan]

Disease that reduces population is not the same as the affliction. As far as I know it is only one particularly nasty summoned creature that causes this kind of "plauge".

Population does not decrease because of bloodhunting, it just causes unrest.

There are a quite a few lucky events that reduces unrest.

Only a Wish spell can increase population.

The Order/Turmoil scale is just that. A decrease/increase in unrest (as well as economic and event bonuses/penalties).