I disagree that the black straps are for any support of the floor. The poles are too insubstantial to serve as structural members. They are strong enough, however, to hold tension on the fabric. The black straps link the poles together so that unfolding the floor opens the tent and pulls the fabric taut.
Your explanation of the ladder angle is spot-on though. The limitations of the extension ladder that comes with the Smittybilt and your CVT are why I swapped in a telescoping ladder from Tepui. It has bigger feet that are able to hold more traction, it's taller, it has a higher weight capacity, and each rung is a point of adjustment, so you are far more likely to find a good angle. They run about $150 and only require the drilling of a single additional hole in the tent floor.