How do I make my displacements go out of the mesh rather than inside the mesh? I'm creating a star destroyer from an older youtube tutorial, and I've gotten to the point of doing displacements on my mesh. My issue is that it seems the UV editor selects the mesh from the inside (when I select a line of faces from right to left, it shows it from left to right in UV editor). This results in the mesh extruding inwards like shown on the pictures. I would rather it extruded outwards. I hope someone can help :)
This can be caused either because your normals are flipped (which is not the case I suppose) or because you auto-unwrapped the model and now you need to change the scale on your UVs (specifically on the face which looks wrong) and on the proper axis (like scaling on X by -1). 
Now for the displacement map, usually a displacement map has one channel (grayscale) which means that if you invert it (add -1 or introduce invert node or remap it with ramp) it should look towards the opposite direction. 
Hope that these were helpful! 

PS: and as you found out and mentioned on your comment "midlevel" property should do the job if you set it on a negative value (like -0.5 or -1)