IMHO, 1st configure a fresh install of debian with all power management turned off. Test it, so that the screen, session time out etc are not active. Once sure, copy all or relaventnt dot files (.config etc) from current user folder, and place them in /etc/skel folder while/ after creating the iso. This way, the configs will be enforced for live user as well. Test. Hopefully your issue will be resolved.
If you don't know how to add the dot files at build time, use any remaster tool after ISO is built to place them manually in skel folder. I have one such script as part of PakOS (kindly search Google for PakOS, it's usually 1st result on sourceforge), A Debian derivative. All code is bash script, so hopefully you can copy paste it to your liking to enter chroot and rebuild iso once done.
Happy Coding
Our ISO image is intended for a CNC controller. It is important that
the display never blank or automatically log-out the current session,
even if left for days at a time with no user input.
Can anyone give me any pointers how to achieve this in a live-build image?
--
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912