My vet called me back just now. The plan is to up his pain meds even more and see how he does. If he's not back to more regular weight bearing on that leg by Friday, then he needs to go in to the clinic.
After describing his behavior she told me it is unlikely that he broke the top of femur (a big worry for me since it is so thin now) or FULLY ruptured his anterior cruciate ligament (in the knee)....but it is possible he partially ruptured his ACL. It could also be that he just bumped or tweaked the hip and it will just clear up on its own. It's hard to say at this point, so we're trying a wait-and-see approach.
Please send prayers and good thoughts our way.
Thank you so much for reading.