Thank you, thank you. ^_^
At 1:45 it's a simple trigger bypass, though one of the dummies likes to often stand still in the corner making it impossible.
As for what happens at 3:23 and 7:53- I described that one page ago. You didn't do your reading again, did you?
I've written a better explanation of it in the text comments for the SDA release:
Segment 31 (01:10:17 – 01:11:12)
I really only decided to utilize the above described after finding that if you save right here, all the enemy triggers in this room...break. If I didn’t save here and entered one of the next squares, two enemies would spawn from the ceiling and upon jumping into the shaft it would open and another enemy would spawn. But since I saved, not only does the game ignore the two jumpers, it also ignores the one in the shaft (is it a shaft? I’ve always had issues telling that in these games...>_>), meaning it does NOT open which not only looks sexy, it’s faster that way.