Looks pretty dense in there, yeah. Well, since the plant did the work for you, I'd forego stressing it out more by pruning or topping again, and just flower it in a week or two. One week if it grows like mad, two if it's slow.

I've never lifted a 3-gallon rootball myself. Well, not when I cared if the plant lived anyway. If I had to do it though, I'd let it dry thoroughly, then flip it upside down and tap the bottom of the pot until it comes out, add soil/stuff to the bottom of the pot, then replace the plant and it's rootball on top of the new soil. If it comes out in one big chunk, which it should if it's dry, then doing this shouldn't shock it much or damage the roots. Bugs me when my soil settles down 2-3 inches too, but I just live with it, maybe throw a little extra on top if I can do it without burying too much stem.