Hi Keri,
To put it bluntly, the AN diagnosis stinks and whatever treatment choice you make is something you don't really want to do, just a decision you;'ve made since you have to make one so doubts are not unusual. My best advice to you is that since you've made that choice dont second guess yourself, you can drive yourself crazy. When I was first diagnosed and started researching this thing, my first gut reaction was surgery, then radiation, then surgery, which I had (translab). I was one of the lucky ones and had a very good outcome, but even if I hadn't, I knew in my heart this was the right choice, no matter what. Once I made that decision I was no longer afraid -- I knew if there were issues to deal with, I would be able to deal with them. That feeling of confidence made the time before surgery a lot easier to deal with. I hope this happens for you.
As for wonky head, you probably do have it, I know I did prior to surgery. If you feel like you are noticing things llike that more now, it its probably not in your head (no pun intended) but because you probably brushed them off before as inconsequential. Regarding running half marathons, first of all, congratulations on running your best time ever. Two months post-op sounds optimistic, but you never know!
Best wishes,
Wendy