Well... Im not sure there is a way to disable herb drop... But try setting the rates (rates.properties) to "0.0" for all herbs... that should make droprate to 0x, thus not drop at all... (im not 100% sure however)
As for npc skill protection... i dont know if this function exists outside of the Oneo release... but atleast there its not a list for protected npcs, there is a list of npcs that ALLOWS you to cast skills on them.
Go to other.properties and at the bottom there should be something called
"AllowedNPCTypes" (once again, i dont know if this exists in any release other than Oneo)
This list is the list of npcs ALLOWING you to cast skills on them, anything which is not on the list, you cannot cast skills on... So here you just add the npc type, for the npcs you wish people to be able to cast skills on.
(For example, the type of the gatekeeper is "L2Teleporter", if you add "L2Teleporter" to the list in the properties file, people will be able to cast skills on the gatekeeper, aswell as all other npc which has the same type)