Resupply by airdrop has usually ended in failure throughout history. There is not enough airplanes to drop the tonnages of supplies needed to keep a besieged force fed and fighting. Just ask the Germans at Stalingrad and the French at Dien Bien Phu.
And when you drop supplies to a bunch of hungry people, without any distribution system in place, they’ll just kill each other trying to get to it.
While GPS-guided parachutes have revolutionized supply drops, I'm inclined to agree that they're fraught with error. Still, the volume of allied air attacks on ISIS positions combined with interdiction efforts against ISIS resupply efforts should be sufficient to stabilize Kurdish positions, if not help them advance. B-1's have been deployed over Kobane. Given its ability to carry hundreds of smart bombs, I'd say the Kurds do not lack for firepower, at least while the B-1 is in the air.
You're right. One of my closest calls during the Vietnam War was one night when receiving an emergency airdrop of ammunition, a USAF C-123 flew the wrong stem of the T and almost put the bundle right on top of me.