Yeah, a lack of a tutorial of any kind of botched the ability to intuitively play this. I slapped a haphazard control layout in the settings menu and also elaborated on the controls on the actual game's page (near the top of the game description).
The minimap was a last second addition and no real thought went into it. It is simply a secondary render target with orthographic view. This is bad for many reasons, but worst of all is that with this method, it doubles up ALL draw calls and by extension the performance requirement. I figured it was better than nothing, since it does show to some degree when enemies are in-bound, outside of your primary view and most semi-modern PC's can still run it just fine. But yes, I agree with your cons entirely.
Thanks for the feedback, Ben!