Hello, the fix is in!
My nano-sim cutter finally arrived, so I’ve activated my phone, confirmed the problem, and then over the last few hours I finally had a chance to work out the fix!
I had made a rather terrible assumption about how the message text was actually sent out, and so the typed message was never referenced properly. 
The updated code and VXD has been pushed to github! Sorry for the silly bug, and please let me know what everyone thinks!
Also, now that the basics are working, I’m curious how other people think I should lay out the keyboard? I just picked the modified QWERTY I used merely for simplicity’s sake and to try and cram as many symbols as possible in. There are many symbols missing however, and I’d like to make it more complete. Capitals, for instance! But given the limitations of the screen size, that’s a lot of different screens…
Thanks for your interest!