In scenario #2, the PAVN 32nd Regiment cannot move until the turn after combat with the AVRN relief column. Reading that strictly, it seems to forbid the PAVN 32nd from attempting combat refusal or reaction when first attacked by the AVRN, which the rules define as "pre-combat actions" and also which allow the units to move. Also reading it strictly, it seems offensive bombardment does not count as combat since it occurs before those "pre-combat" actions.
The SSR seems intended to prevent movement, but it also appears to prohibit refusal/reaction. Is that correct and intended?
Combat Refusal is a retreat, not movement.
Defender Reaction is movement and prohibited to the 32nd.
A Combat Declaration is sufficient to count as combat in this instance. I'd also say if you Bombard them, they can move.
The intent is that they "ambush" the relief column which releases the US forces.