Terraria – How to get vile powder

If you are on the left of the exact middle of the map, he will go the left toward you, and vise versa. Possibly try looking both ways when trying it.

You could try making your room invalid temporarily.

An example would be replacing the floor completely with platforms.

Once that is done the NPC should pick a different home to live in, go somewhere else in the world for a day and come back and they should be elsewhere (I think day/night changes cause NPCs to warp home).

I believe you should be safe to fix your room once that is done.

This page has all of the details about how houses work and you may be able to use that to modify your room to be invalid by that measure.