Hi Dupe
I too have a PSR SX700 and I do use the full version of Mobile Sheets, however I use it with a Lenovo Android tablet, but I don't use any kind of cable, so not much help to you on that.
Mine is connected by Bluetooth and is a Lekato © Pedal. The pedal is set up quite independently.
What pedal are you using?
I chose this combination so that I can simply change keyboards without having to use cables, as I also play a Korg Pa5X and it's easy to just put the pedal under either keyboard and play. The pedal and Mobile Sheets are automatically linked, and work seamlessly by Bluetooth.
I’ve no experience of using midi files. But I have got many thousands of them going back about 30 years. It's just something I never got into or learned about.
Page turning has become a dream since I transferred most of my pdf music to the tablet. I play from music scores, with both hands and the full keyboard. I also play from many physical music books that I own. I sight read, and play by ear.
I'll follow your post with interest.
Keith.