Hi,
Couple of thoughts. First, every rabbit carries Pasteurella....and so does every other mammal in the world (including humans).....and many birds carry it. It is an "opportunistic" bacteria. It lies dormant, I think the term is subclinical, until something compromises the immune system. It takes that "opportunity" to show itself.
Next, is there any way to get some radiographs of the skull? The symptoms you posted can be numerous things....but your post concerns me quite a bit. I would certainly be looking for something dental but still be open to other possibilities. In this case, I would seriously consider using Chloramphenicol....and I would suggest asking your vet about using this drug. Some vets do not use this drug. In that case, I would highly suggest using a Pen G/Zithromax combo. But there needs to be a clear diagnosis on this issue.
Randy