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?
   

g.setFont('6x8:5x9') is slow, maybe

It shouldn't be - the call itself will be fast, and upscaling the built-in font should be reasonably quick

Bangle.on('touch', function (b, xy) { xxl.stop(); }); does not really work.

It should - maybe add some prints to the rendering function and see if it really is taking ages.

Must I undo the setWatch

Not with load(), no. You'd asked on another post about vars, but basically load() tears everything down so you don't have to worry.

My drawing routine can do about 30 fps, so somewhere there is a bottleneck.