Thank you for rescuing this bunny!
The first things to look at when deciding on a bun’s state of health is appetite and poop. Alertness, stance and tendency at interaction are also important. Sometimes a bunny that has gas pain can stamp its back feet, and that is serious, but walking on the spot with the fore-feet is not sth I recognize having heard of in buns.
A bunny that isn’t feeling well is reluctant or, often, completely unwilling to eat, will try to hide from sight and will lie or sit still and it will look uncomfortable, sometimes actively pressing its tummy against the floor. Often poop size and amount are diminished compared to normal.
If it’s anything like when a puppy “foot-walks” while nursing, it’s not sth bad at all, it’s associated with well-being and oxytocin-realease (“pleasure”-signal substance released in both mother and kit during nursing).
How does he seem to you? Can you hear any noise from his tummy? Does the tummy feel nice and soft to the touch?