I believe that it is centered. I have ridden many miles without any problems with this setup. That's the strange thing here, nothing has changed! I didn't touch the front wheel after the flat, I just noticed the problem then. Before that, there was definitely no issue.

Could I have damaged the fork dropouts somehow or the fork itself? I go over some rough roads and big potholes with the 23mm tires and the front wheel has non-overlapping spokes.

I will fiddle with it some more. Further suggestions are appreciated. I'd like to avoid the LBS if at all possible since the LOCAL bike shops are not that great and I don't have a car available to drive the bike to a good one.