To answer your question, no a Pandora Battery (jigkick) once modified can only be used as a a ways to enable external reading off an MS in diagnostic mode. Now with this you can run a separate firmware off of your MS. If you don't plan on using the Pandora again, when creating it, you can set it to restore itself to a regular battery after recovery.
A Slim PSP cannot run 1.50 anything. DAX has made all the newer CFWs compatible with Slims, and they can add 1.50 options to Phats.