When my rabbit is in pain from sludge/stones she does angieluv stated and will shift positions in her litter box while trying to go. She will also look like she has gone and 2 seconds later go back to her litter box to try and go again. She will also go on the floor where she usually doesn't go. Where she will do the shifting, she will lift her butt higher then normal, and keep trying to go on the carpet. I also have found that she will lay in weird places that she wouldn't normally lay. She won't want to move much. Won't run around and play. If the pain is really bad, she won't be interested in eating. Those are the things I have noticed.
My rabbit would grind her teeth in pain laying in a bunny loaf position. But she wouldn't get up run around and play.
For rechecks, my vet usually does an x-ray. Though I had one vet do an ultrasound. We have also done the lab work including the urinalysis. If they get a good urine sample they can check the calcium content of the urine. I think having all the tests you listed done is good. That way you can see if anything else is off.
Good luck at your appointment.