We went back to the vet for a checkup and to remove his stitches. So far, he's doing really well. We saw a couple of other dogs with the same haircut and back scar, so he fit right in. (That's him looking expectant in the waiting room this morning.)
Ollie's going to do a little hydrotherapy over the upcoming weeks to strengthen his muscles. That should be interesting! A side benefit is that he'll get used to the water, which will be handy for his upcoming Aspö summer.
I haven't heard from Wille yet but I hope to soon, and will report quickly.