There is no way to directly macro movement. Why not just turn off Click to Move on your Hunter?

As for why interacting with NPCs is sporadic, I have no idea. I don't know how AHK works and I don't know what your AHK script even looks like (I've been able to read minds in the past, but I'm getting older these days). Seeing as Interact with Target is a key binding in WoW, it's either going to work or it isn't -- It's not a 50/50 luck-of-the-draw feature. That would indicate to me that your script is either messed up in some way, or you're just not close enough to the NPC to interact with them.