@reyalp a lifetime later...
Thanks. It'll take me a bit to get back up to speed with this, I've been distracted with PTP bugs (which I initially discovered because one of these scripts was exactly the size required to trigger it
)
The first 10. Are these what you expect?
Used a white surface on a computer screen as the low contrast scene, think that'll fare ok but still mentioning it as it's not a wall. All walls are black at night 
Yeah a computer screen should be fine, as long as it doesn't flicker significantly with the shutter speeds being used. Doesn't seem to be a problem in the ones you posted.
There are a couple oddities:
ixus700_sd500
only has the header row in the CSV. Seems like maybe the script errored out before it took any shoots. I noticed the date was 01/01/1980 00:00:33 so it could have been sitting at the clock screen or something.
It would be helpful if you can re-run and check whether it actually shoots and if there are any errors on the camera screen.
ixus970_sd890-100c
From the log, it looks like the ND was in for the initial shots, but not in the initial half press. This is weird.
Please check whether ND is set in CHDK overrides (it should be "off"), and if it was already off, maybe retry with a darker scene. A wall can be pretty dim and still work, a 1 sec exposure would be fine.
