i assume you realize it in one of the backlog episodes but the triple stack you unlocked is for the warrior bow you use the hunter bow hunter are the shorter range ones and warrior the long range one (if i remember correct, could very well be i am mixing them up)
ah that's a bit annoying; There are a few caveats. Auto-pickup won’t work if your inventory is full, and you need to send the excess loot to stash. It also doesn’t work on fallen enemies or chests.