Is the SD750 starting in play mode ? This would normally be the case, since it has a play button rather than a multi-position switch like the sd1100.
In that case, you should make use the script to make it switch to record mode. You can do this by sending a click "shoot_full" or set_record 1. You will want to have a wait after that, to allow the camera time to switch to record mode. You can see setrec.bas and setrec.lua in the SCRIPTS/TEST directory for examples.
Not sure about the other issue.