M, I find your experiments and experiences interesting and informative, the pictures displaying a similarity to various points in Beshine's journey. One can see your natural posture adaptions to the increasing weight. Your ending 17" "depth," which I assume if projection, exceeds the 13.5" that I have estimated Beshine's current projection, while your 24" width falls short of the 27.5" I have estimated Beshine's to be bralessly; perhaps it is closer when her boobs are also squeezed into a bra.
Obviously, Beshine's boobs are not actually spherical in shape; they have a perhaps 7.5" flat surface where they are against her chest wall. So calculating the volume with the assumption of being spherical would give you a false low; the shape actually being more like a partially filled sphere. Regardless, at her size, a mere 1" difference in average diameter, even assuming a spherical shape, yields a 5,000cc difference. If I were to do a calculation based upon a average diameter of 14.5" (your 17 + 24/2), I would get a volume of 26,159cc for a sphere or if we just went by the 17" alone, we get 42,155cc. At this size, small increments result in major changes, harkening back to the geometry that doubling the size of any 3D object results in a volume 8 times the original.
Your final pictures do reflect a size similar to Beshine when she is wearing a bra, maybe just a bit narrower, but the projection appears close; with arms reaching forward in her natural shoulders back standing position, her projection is close to the middle of her forearms. Extending the shoulders forward seems to decrease that by maybe up to 2". You can find pictures that support this, with her elbows well short of her projection when standing upright, shoulders back.
Doorways, I have to assume that is was a 27" door; interior doors seem to come in 4 widths. I have no idea about European doors, but we do know that Beshine has said that she normally angles through doorways because her boobs are too wide to walk straight through. Kinda like the chair thing; the standard seems to be 22" seat with 24" between arms and we have seen that when seated in a dining room chair, her boobs extend laterally past both arms. And resting on the thighs is all a matter of posture; upright, I think Beshine's are a couple inches above her thighs, however, she is usually at some degree of leaning forward to the point where they rest on her thighs. If you think about this, it is like standing, a normal stance put the burden on the back, so we see her lean forward when sitting, a logical approach.
A sticking point on all these guesses is always volumes. Lolchair once did a similar thing, filling balls within a bra and posting that it took him 19k to create a look similar to that of Beshine at the time. That was like in 2013 and personally, I would have guessed her to be 13-14k at the time, but his experiment was generally accepted. It is certainly subjective.
The weight is certainly even more subjective and it is something that Beshine has had 20 years to gradually get used to the increasing weight. Neither you or I could stand after being suited with some sort of outfit that brought our weight to over 800 pounds, yet there are many essentially homebound women who weigh this much and more who manage their weight daily. Like Beshine, they had years to adapt to their increasing weight and where I would ballpark her total weight to be maybe 230, she is far short of 8 or 900. Having the weight secured to her bone structure was a smart move; mounted high, it is easier to carry, the center of balance maintained by posture rather than muscle strain. I absolutely do believe that if you had to wear that rig 24/7 for an entire year, your opinion regarding the weight would change dramatically. Even if it were just a half dozen hours each day, you would quickly start adapting. It is like riding a bike; if you haven't ridden one in years, you will feel the burn of different muscles than walking, but within a short time, that goes away.
But like Malik said, the weight and size only comes into play when we try to rationalize the effects on every day life. We don't see the results of this as often in OF videos as much as she used to do, emphasizing her massive boobie adventures, which I have always liked realistically imagining. I love your practical approach to recreating the Beshine experience and as we have seen, it can be quite enlightening; just trying to do simple tasks becomes less simple when you cannot reach both hands around your boobs to do something, but now much reach over or if it can be achieved with one hand, by turning to one side enough to move your boobs out of the way. A day of entertainment, and then you want to lay of the sofa and watch TV, only to find that the weight is substantial, but your position choice is hardly negotiable.