I use a very similar set up, except I use an Android pad in to control the katana and a separate old iPhone plugged in to it. No Bluetooth. With a jack splitter at the katana headphone out, I can listen to the guitar, the Android and the iPhone all at the same time!
Question for @jsgreen
There is this thread here asking about the katana and difficulty setting up with Mac. Would you consider adding your input, since you successfully installed a Mac katana driver? Thanks!