i have a little bash script that i use to launch the app. it is in its own subfolder, with another folder next to that titled Bitcoin.:
#!/bin/sh
PWD=`dirname "${0}"`
cd "${PWD}"; ./Bitcoin-Qt.app/Contents/MacOS/Bitcoin-Qt -datadir=./Bitcoin
put that in a file, make it executable and there you have it. hopefully you can figure out how to change the location based on that