Hello superdave !
I agree with you, Ed' (the french guy that is on the video) is incredible !
Here we go for the answers :
1) You can save/load a project on your iPhone and export a saved project to your computer through a http based server integrated in the app.
2) If you use an iPhone, you don't need an external mic at all. You are totally right for the feedback and also totally right with the solution, as long as the external speakers are not too loud or too close to the iPhone mic of course. The best way of doing things is simply to use headphones, as Ed' does on the video. Plug your headphones/speakers, then launch the app and voilà, the internal mic will be used for recording and the headphones/speakers for outputting sound
!Have fun !