The SS division HQ was indeed in the rear, at the beginning point of the highway when I destroyed it. I attacked from the east at night.
The force delay difference was a misconception, as I re-read the manual, there may be a difference of about 10 mins, impacting two units, which did not make a difference in my case, in retrospect.
Note, the diagram here and my previous AAR are not from the same attempt. I will update new AAR later, and I figured I could more or less get a consistent result now.The key is to use the infantry of TK Kane to interdict them. I tried about ten times before finalising this deployment map. Changing it will most likely cause the loss of Grandmenil, or possibly worse.
In the diagram, circles are positions to hold. Yellow line are moving routes, and red ones retreating routes.