You said "It seems that this port doesn't support focus scan and optical zoom during video recording - probably for a good reason."
While I am retired now, most of my career was in shooting TV commercials. I can't possibly think of any "good" reason for the above, which eliminates 2 very required features of a video camera.
I suspect what srsa means by "Good reason" in this case is probably that it was tried, crashed and nobody figured out how make it work. CHDK is a hack that pokes at the poorly understood guts of an undocumented system.
Also, locking the iris was supposed to be a feature of the SX130IS before CHDK is installed. Does it get lost after installing CHDK?
No, CHDK does not disable Canon features, unless it's a bug in the CHDK port. IMO, it would be fairly unlikely for a CHDK bug to cause this symptom, so this problem is probably between you, Canon and perhaps the Canon manual.
Also, you mentioned being able to then focus with the zoom lever in ALT mode. ?? You mean to get the CHDK menu back and then focus? That isn't clear to me. Can you help?
Yes, if this feature were enabled on the CHDK port for your camera, you would
1) set SD override in the extra operations menu
2) leave the menu
3) When you want to adjust focus, go to alt mode and move the zoom lever. You can use the left/right arrows to adjust the size of step.
However... this feature is not generally enabled on CHDK ports for cameras that have MF in the Canon firmware, since it was intended as an MF replacement. This is something that we should look into improving.