It could be several things, so I’m glad you are bringing him back to the vet as soon as you can. I am only speculating here, so don’t take this as medical advice.
In the meantime, watch him carefully and assist him with things like moving, getting into his litter pan, eating, and let him rest. If he gets worse soon, call your vet to describe his symptoms and ask if it’s an emergency.
First, it may be a re-occurrence of the ear mites. I urge you to keep him indoors, possibly for good, to avoid getting any more. If you don’t know where they came from, they may be from where he was outside. It’s perfectly OK to have a totally indoor bunny who’s never been out (I do). They feel safe inside, get clean food and exercise, and can relax. So don’t think you’re depriving him by being a House Bunny.
Another possiblility is that he has a disorder called Head Tilt, which is very uncomfortable for a bunny, but treatable. If it is that, you can prop him with some pillows to keep him from falling over and stop the dizziness. There is more info. on head tilt on the site, but I hesitate to have to research it until you have a correct diagnosis, since it can be a scary illness, and I don’t want to alarm you more. Let the vet diagnose it.
Finally, with a leg disorder from before, he just may have injured himself again and is struggling to get his bearings. Again, help him to stay off his bad leg and stay settled and comfortable until he can be examined. Does your vet have any Saturday hours? You may want to call today in case he can be brought in and left there for a thorough exam and beginning treatment. We really can’t tell via the internet, but with a bunny a disorder can progress quickly, so just a phone call to your vet may bring you some relief until Tuesday. (The vet may be able to rule out head tilt, or tell you what to watch for and how to make him comfortable.)
Sending {{{{{{{{{{{Healing vibes}}}}}}}} to duke.
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