There is no 'probably' here as in 'probably more objective to say the middle 1/3rd is shorter than the lower 1/3rd'. You didn't show what I asked you to demonstrate (division of the 1/3rds on your ceph). So, the only 'probably' conveyed to me is you either lack the basis to do that or don't want to process information objectively. So, no basis demonstrated to be built on by addressing other questions. There needs to be some demonstration of basic understanding for me to build on if I am to answer questions lest the person process the information incorrectly through a FEAR FILTER and then go about trying to micro-manage the displacements the surgeon does and with no basis to understand what they're asking for.
If your doc is a good guy, he WON'T be performing anterior impaction to someone with a short maxilla and little tooth show. So, question #4 is a MOOT one to even ponder. Crossed of the list to address.
'dammit daniel' in another thread told you the drop down to the maxilla is a distance increase in the facial height that is seen at the lower 1/3rd. Yet you ask the SAME question again as to whether the downgraft will lengthen the midface. Was already addressed. So crossed off the list to address again.
As to questions #2 and #3, it would be silly to make any requests in the absence of demonstrating you can produce a diagram where lines are drawn through the right places for the division of '1/3s'. Again some basis for understanding is needed to be built on. However, the relationships would be SELF EVIDENT to someone who knew where to draw one set of lines because not too much of jump to find the line of the occlusal plane, measure the angle relative to a horizont, determine if it's 'steep' or 'low angle' and then determine which rotation increases the steepness and which one decreases it. As to whether or not a uniform graft changes the occlusal plane, it's the same as asking if putting a uniformly even block of something on any plane would change the angle of inclination of the plane your putting it on. 6th grade geometry. Moral of story...if those relationships aren't self evident to you the answers to those questions (given to you by someone else) aren't grounds enough to make requests based on solely the answers to the questions.
So, all 4 questions can be disregarded. But no preclusion for someone else to answer them.
Your ceph reveals you are a low angle patient (low occlusal and mandibular plane) with a SHORT face. Your doctor told you your overall aesthetics (including the nose and nose to lip angle) would improve with BOTH the forward and downward displacements. He most likely SEES on your ceph your face is short due to not enough downward growth of maxilla.
All you've demonstrated here is a belief that your midface is long and a fear it will look longer to you in the mirror. Ultimately what you really want to know is whether or not you will like what you see in the mirror; whether or not you will look like how you want to look in your mind's eye. THAT question can't be answered here. If your fear is that your midface will look longer to YOU via the aesthetic IMPROVEMENTS your doc is willing to perform or you need an answer as to whether or not you will like what you see in the mirror, have your doc tackle that fear. If he has any reason to believe you would be UNHAPPY with an outcome aimed at improving your overall aesthetic, he might elect to limit to the single BSSO or he might have some other way of tackling the question 'Will I like what I see in the mirror?'
In the meantime, here's a link to SHORT FACE GROWTH PATTERNS where you can look at patients who have somewhat similar growth pattern to maxilla you have and see if their midfaces look longer to you.
https://pocketdentistry.com/23-short-face-growth-patterns-maxillomandibular-deficiency/