[thejeff]

2) Jade Knife helps with blood sacrifice, not hunting. Sanguine dowsing Rod is what you want. Higher the blood level the better the hunter, but there are diminishing returns. If you've got cheap B1 mages it's usually best to use them with a Rod than use a more expensive mage.
The general rule of thumb is 3 B1+Rod hunters per province.
Unrest figures in, so lowering taxes or patrolling helps. If population is under 5000 you also get less, so it's best to hunt in provinces far enough above 5000 that they'll last awhile (dependent on scales/unrest/patrolling) but low enough that you're not losing too much income.
As far as I know, returns only drop over time as the population drops.