Are you sure all your settings are correct?
I'm not an expert on how the scaling works, but I think you're misinterpreting how the 'units' in Superpowers work.
Each 'unit' in a scene is just... 1. They represent 1 square / cube of a 2D / 3D game world. It's a simple graph representation essentially. Setting the 'pixels/unit' on an image / cubic model / whatever, tells Superpowers how many pixels of this image / texture will span across 1 unit in the game's scene.
Again, not an expert on all of this, so that may have been a lousy explanation. Sorry bout that.
However, I did manage to get the 160x144 resolution working in my game, so I'll show you my settings:
Hope this helps, let me know if you have any other issues or need a better walk-through of this! :)