Ok just to make sure I understand correctly.
1. No attacking the rear arc in CC.
There is no bonus or penalty for attacking from the rear, therefore the point is moot. Only when attacking vehicles is there a bonus when attacking the rear arc, and then, only with AV-rated weapons. When attacking any other model in CC, there is no "rear" arc, as all models involved are constantly changing position within the melee.
2. You can force a person out of a tactical position by attacking in CC with a unit that would force him to turn.
I am not sure I understand your meaning here, as there is no position change, other than facing, which is free and unlimited for models that are on foot [edit]
while in CC.
3. If attacked in CC by two or more units, I MUST spend an action to turn to attack the unit to my rear < even tho CC is a whirling mess>
It costs no AC's to turn to face the model(s) that is (are) attacking the turning model in CC. There is a cost of turning to fire at a closer model in your rear arc, asFiring Arc is 180 degrees, but sight is 360 degrees, therefore, a model that is out of your firing arc, but is in LOS and closer than a model in your firing arc must be fired upon, according to target priority.
4. The Scorpions shield protects both combatants if outside fire is directed into CC.
Do I have that right?
GFQ, man. Never gave that one much thought. Let me get back to you on that.