You hit a lot of nails on the head, Miggie. With sideboobs extending as far as they do, I have serious doubts that she can crawl on all four because her arms are trapped at shoulder height or even, as we usually see, extended further forward.
And yes, it seems the common theme in her video descriptions is about the weight. In past years, she would often remark about the increase in weight after a fill, saying it takes a few weeks to get used to it, and then a few weeks later she would start wanting more. I have remarked before about her facial expressions, the heavier breathing, and the way her boobs cause her whole body to quake when she bounces; it is all a departure from the ease exhibited 10 years ago. You can see how carefully she moves when trying to get on her hands and knees, always using things for support. I have even caught her facial expression showing the effort of slowly sitting in a chair with arms; no doubt a necessity to protect the boobies.
In one video, she talks for a few minutes about how the movement of her boobs is challenging in a few ways, including balance, chafing, and drawing unwanted attention. In a number of videos, we see the care she uses to merely step down a few inches, and though we seldom saw how much her braless boobs wobble out of control under a loose top, she does say that she would never walk in public without at least one bra. That said, she does seem to enjoy going braless when walking outside in places without crowds, which just supports her contention that she loves the feeling of her enormous heavy boobs moving on her chest when walking. It must be like having two 50 pound Jello domes wobbling.