^ 50/50 It depends on the price, if you make it to high everyone will be making thousands easily. Maybe $5 or less.
Support. It wont ruin the economy if you make it cheap enough but arrows are practically useless. $2-$5 a stack wont hurt at all.
Right, bones would still be the primary source of income when killing skeletons, but instead of throwing away all those arrows you get when you grind them, you can just sell them for a bit of extra cash. It's not absolutely necessary, but it's not pointless.
Support, as the people above had said, if they are sold $5 or less a stack, it shouldn't ruin the economy.
I don't play on org, but this sounds like a good idea as long as it's cheap. It sounds like a good way to get rid of excess arrows.