Finding the carrier:
As in Real Life, the carrier moves. SF's code was originally written with fixed airbases in mind, WoV added carrier ops, but as you've discovered, they're not fully implemented, even with SP4. Perhaps TK will address this in a future patch, he has stated in the past that he might.
HUDs:
Vietnam '84 was released well before WoE and the SP4 updates for SF & WoV, so you're dealing with older models that use the original avionics code. The updated code allows for much more sophistication in the way of HUDs, Radars, and RWRs.
AAA/SAM activity:
The issue here is probably one of both individual model-data.inis for the SAM launchers (specifically, their in-service and out-of-service dates), and the dates that SAM sites are active in the VietnamSEA_Targets.ini file.
Locate, downlaod, and install the updated SAM pack, which includes both SA-3s, SA-8s, and SA-9 launchers, all of which the Vietrnamese would undoubtedly had in operation during 1984.
Feel free to drop me a PM if you require further assistance.