Please note, my capitalizations of certain words are to indicate Titles and should not be consider 'yelling'. I am debating the issue not angry or upset.

Also, no need for forgiveness but I think you departed from the rules at a critical point and the rest of your confusion stems from that point.
Forgive me if I'm wrong here, and maybe I'm misundertsanding you Seamus--
Enker wanted to know if the squad could use all of their actions after the vehicle/crew had used their three actions. The answer is no.
But it seems like you're saying that after the vehicle moves only 1 guy can disembark because he's blocking the door???
Only if the scenario painted by Enker is used. If the vehicle moved 1 action then all of the squad would then have all three actions.
What's more confusing is that everyone seems to be saying that the troopers in the squad disembarking only get 1 AC???
No, they can have all three actions but actions while in a vehicle are used simultaneously. For instance, lets say the APC has a driver, a gunner and 6 models inside being transported. The 6 models while inside the transport count as a single unit, the passenger unit. The passenger unit has only two options, ride or disembark. Each time the driver and gunner and expend an action, every model that is being transported also expends an action even if it is only to ride. There is a time element introduced into the game by these simultaneous actions and it was done largely because of the ability of a few vehicle models in 2nd edition to create a situation where the pilot/driver of the vehicle could move move move then the gunner could then shoot, shoot, shoot.
Here is how I believe it is meant to work based on everything I have read and have been taught by one of the rule designers:
Action 1: Driver drives, gunner fires, passenger unit rides. This kills the first action for all units in the transport.
Action 2: Driver drives, gunner fires, passenger unit rdies. This kills the second action for all units in the transport.
Action 3: Driver drives, gunner goes on wait as their are no targets, passenger unit receives orders from their leader to disembark. However at this point, they only have one action remaining. We now switch over to the rules for disembarking. It costs one action to disembark, which is performed by placeing the model at the entrance to the passenger section. This costs 1 action. Additionally there is a rule which states if the entrance to the passenger compartment has a model in front of it (friendly or foe) then no one else can leave until the door is unblocked.
Ergo, don't disembark on the third action because the first guy out the door blocks it for the rest of the squad. Instead stay inside and disembark during the first action on the next turn. That way your squad inside the transport have all three actions available to them.
To me this discussion breaks down into 2 areas.
1) Does the boarded squad activate as part of the vehicle's activation.
2) How many actions and troopers can be used during a disembark.
I agree with this however, on point 2, I was answering a specific question.
Let's begin with pg 89 first - 3rd parapgraph - "Operator and Crewmembers are activate at SAME time and can alternate the performing of actions. They are considered a SINGLE unit." (NOTE: my emphasis)
It also says "the order in which these actions are performed is up to the player...All that matters is at the end of the Vehicle's Turn, the operator and ALL OF THE CREW have taken ALL avaliable actions."
This is the crux of our difference in opinion and where I believe you erred. The paragraph you quoted takes place in the introduction to the vehicle section and is attempting to summarize how a vehicle operates but has instead introduced verbage that clearly contradicts a BASIC GAME RULE that is laid out in SECTION 5, USING ACTIONS; page 40 near the bottom of the page in the VEHICLES AND USING ACTIONS section which states: " . . . any crew riding within it [Vehicle] must expend their actions simultaneously. If the driver uses his first action to drive, any other crewman must spend their first action before the driver can spend his second." It clearly states here in the basic rules of the game that all components of the vehicle must expend their first action, then their second action etc. simultaneously. In the second paragraph under that, it talks about models inside a transport, " . . . are considered part of a single passenger Unit. This passenger Unit takes actions just like an additional crewmember. During the passenger Unit activation, one or more of the transporting models may elect to disembark by spending one action . . . See Armored Personal (SIC) Carriers for more detail."
So we've learned that everyone in a Vehicle Unit (driver, gunner, etc.) during this Vehcile's Turn gets ALL their actions. Except for a very small number of exceptions, I think we can all agree this = 3 AC.
So now the key question to me is - Is the boarded squad now considered PART of the crew or a SEPARATE unit?[
The boarded squad is a part of the crew with a limited set of actions to two: Ride or Disembark per the rules I just quoted on page 40.
If the boarded squad is PART of the vehicle's crew than it would get to use it's actions (all 3) DURING the Vehicle's Turn. I.e. It could spending 1 AC to disembark and the remaining 2 AC to move, fire etc (Again, as part of the Vehicle' unit's activation). Moreover, it could use all their AC at any time during the Vehicle's Turn and as many in a row as it wants.
This is where we disagree. See above.
If it is NOT part of the Vehicle's Unit, than the boarded squad would require a SEPARATE ACTIVATION (which would make having a hero/officer on board your vehicle more useful and staretgic since as part of the vehicle's turn he could essentially activate the boarded squad and order them out) in order to disembark. Yet it would still get all 3 AC. 1 AC to disembark and 2 AC to move, etc.
They are clearly a part of the crew.
Now, if we check out pg. 90 Section 2.0 - The boarded models are "considered PART of the vehicles compliment." One COULD assume this phrase means = to another crew member, and therefore entitled to ALL its actions as any crew member would, on the Vehicle's Turn.
However on pg 91. Section 2.1 we read - "While in the transport, Squads being transported are considered a SINGLE passenger unit. Here the word UNIT. Stands out to me. It is not a crew member but being referred to as a sepearte unit. Furthermore, later we read, "...during the PASSENGER UNIT's ACTIVATION, one or MORE of the squad may choose to disembark."
Here the squad is not only referred to as a UNIT, but it is also has a specific, and separate, "ACTIVATION" phase.
To me, this says the boarded squad is NOT part of the Vehicle's crew and therefore could NOT disembark during the Vehicle's Turn.
It is a separate unit and need to be activate separately.
HOWEVER - As shown above, once activated (whether on a later phase or by a commander), it would only need to spend 1 AC to disembark at which point the troopers on board would have 2 AC to move clear of the door and make way for others.
(We read in section 2.2 - "the Passenger unit needs to spend 1 AC to disembark" = this unit would then have 2 MORE actions.)
So, to me what needs to be clarified is..."considered PART of the vehicles compliment."
Does the term compliment here mean = to a crew member or not.
If yes - then the language "PASSENGER UNIT" and "PASSENGER UNIT ACTIVATION" should be changed.
D
The rest of what you say is clearly resolved by what I consider the actual rule concerning the manner in which a vehicles crew expends their actions on page 40. Your entire argument hinges on that rule and the supposition that the transported squad is separate even though page 40 clearly states that this 'passenger Unit' takes actions just like a crew member. I look at the 'passenger Unit activation' stated on page 91 to refer to their phase on each succeeding action not a separate unit being activated. They don't become a separate unit until the turn after they have disembarked. I think certain verbage in the Vehicles section could have been worded better to bring it in line with the rules in Section 5 on using actions however when read in context with those rules, the meaning becomes crystal clear in my opinion.
To summarize, I believe that what I have said is right because:
A) Page 40 is a part of the basic rules and outlines how to use actions for all types models and so supercedes the verbage you use to indicate how a crew spends their actions.
B) I know from conversations with one of the rule designers which I believe can be verified by Coil, that an attempt was made to tone down the power of vehicles from second edition and prevent the usage of actions by what are essentially components of the same model in such a way that it gives them an unfair advantage.