I am no longer in a Halo brace but now in a cervical collar (Philadelphia collar), waiting for a call on whether I need surgery after all. I had thought that was ruled out, but if the still-partly-open vertebra opens further during neck flexion and extension, apparently I'll need surgery.
UPDATE: NO SURGERY!
But I no longer have my head bolted to a framework, which is awesome. I will now be able to shower in a more conventional way, albeit with a shower cap because the holes from the skull pins are still open; in a week or so I should be able to shampoo my hair. (It's been cleaned with no-rinse "astronaut" shampoo but it's not the same.)
UPDATE: It'll be a year before I can get back to Aikido. I will probably go back to Kung Fu and see how my knees hold up. I'm not supposed to wear the Philadelphia collar all the time; PT is me trying to hold my head up and move it around, get my range of motion back.