I think there is an error in your diagram. The switch above should be an SPDT switch and not a SPST switch. That way, you can have one pole wired to your ignition switch just in case you want to power it up using your key with the other pole being used if you want to apply power by bypassing your ignition switch. But, if you bypass your ignition switch and forget to open the SPDT switch, you will drain your battery down when the car is not running.
If you use the controller listed above then you should not have a problem surviving crank (This information is listed on the associated web page for the controller).