Well, I think he knew Walts name from what was going on.
As for the invasion of the body snatcher, I think whomever was in the cabin was kept at bay from the ash that surrouned it. This, though not a subject matter expert, the ash that is tends to keep things out or away a protective or a circle not allowing the entitity to leave. As we do not know if Jacob or Man Number 2 is good or bad I would guess that they did not go after Locke immediately.
I still believe the island has a larger role and we have lost sight of this with the introduction of Jacob and MN2.
I think Locke was taken, in the sense he was at one with it, by the island because it cured him. It allowed him to walk again. Remember Rose and John both stared at the ocean, contemplative and very engrossed.
I am not dissing your thought, it is great, just sharing some thoughts I have had about this myself.
From the start Locke was very involved with the island and well, it could have been from Jacob touching him and that was his level of comfort and awe of the island.