A) Are Wild Weasel air-units that support a detected airborne/airmobile mission also subject to SAM and AAA fire? Or do they go to the Flown box before ADF is resolved?
Yes, when firing SAM/AAA you roll against WW too. Escorts are not attacked.
B) I'm assuming that airmobile movement that is not detected (by local ADF) is not subject to AAA fire, since no damage can be caused by local AAA, and any Abort result would be meaningless post landing. Is this correct?
Yes, if the mission is not detected by either Local or Normal ADF it's successful
C) Is ADF resolved against each individual ground unit that uses airmobile unit (post detection)? In other words, if a stack of 4 airmobile units is attacked by SAM fire, would I roll once for each unit?
If you move them all the ground units in one stack there all on the same mission, and there's only one ADF roll per mission. But you could also move each one separately, for more chances of landing something.
D) If a lone HQ is attacked, could it support itself (therefore increasing its defense factor by +4/+5). In a similar vein, could a division HQ receive HQ support from its corps HQ? Finally, are supply depots and MSUs eligible to receive HQ support?
In order to be eligible to receive support, the attacked hex must be within the range of the HQ providing the support and at least one of the units involved must be subordinate to the HQ providing the support. An HQ cannot be subordinate to itself, so it can't support itself. But if an HQ being attacked is subordinate to another HQ, that second HQ could support. Like an ROK Army HQ.
I'm not 100% sure about the Supply Depot/MSU part of your question. So I'll let another chime in.
Hope this helps