make sure the alt+ keys are disabled
What about removing all of the buttons on the window so it canβt be closed or lowered?
Remove all bottons does not help, for FF could crash by visiting some page. I think you can use a cron job to monitor firefox process. and restart once it died.
Or maybe you can make a sh script to start firefox like:
#!/bin/sh
while :
do
firefox
sleep 10
done
Then call it in .xinitrc