Re #3 — that’s on me 
I was trying to resize the black box right in front of me to reach the platform. I didn’t use Q/E at first, just left-click + scroll, so it looked like it changed size but it was just visual.I was trying to move the box around and found it kinda hard to turn, but I realized later you don’t really need to do that anyway.(as above)
The black box can’t actually change size. The right way is to grab the blue box that drops, resize it, and use that to get up.You can ignore my third comment then — I jumped back in and checked. All good!