Hi, thanks for purchasing and playing! I'm glad you enjoy it for the most part.
Remappable keys are a major planned feature. Other than bug fixing, it is my top priority right now. At the moment, the game emulates a 640x480 display that stretches up to at least 1920x1080 in fullscreen; it originally forced the display to a true 640x480 resolution, but this has caused some problems on some systems. The plan for the final Steam release is - if it does not create major problems - to include multiple resolution settings.