new app "XXL Messages" - need coding advice

I made an app that replaces the MessagesUI app for people with bad eyesight. So it just displays new messages with a large font and when you push the button, you return to the clock.
Here's the beta-app:
https://kungphoo.github.io/BangleApps/?q=xxl
Here's the code:
https://github.com/KungPhoo/BangleApps/tree/master/apps/xxlmessage

My issues are:

1. When the message scrolls and another message arrives, I think, both messages are displays simultaneously, which causes a slowdown.
   
2. g.setFont('6x8:5x9') is slow, maybe? Is there a way skip loading the font again and again for each frame to render?
   
3. Bangle.on('touch', function (b, xy) { xxl.stop(); }); does not really work. I think the drawing keeps the CPU too busy.
   
4. Must I undo the setWatch(xxl.stop, BTN1) when I leave the listener with load()?
   
5. I put all code inside a xxl {} structure. Is there a better way to do this? I was afraid of using global variables in a listener function.
   
6. Is there any way to speed things up?