NJWilliam says:
How is retrieval of arrows, quarrels, and sling ammo being handled?
Generally, if the situation suggests that it would be possible to recover an arrow (e.g. if you were firing in a reasonably constrained space, or it's sticking out of an orc), then I'll let you retrieve it. But there is a 1-in-6 chance that any arrow fired is broken or lost.
There is a fletcher in the kobold market in Stonehell that sells arrows and bolts, so there is a source of resupply.