I had an unaccepted question for several weeks that I finally abandoned hope of getting a working answer to (A non working answer had been given). I deleted it, hoping my accept rate would return to 100%, but that doesn't seem to have happened. Is it stuck like this?
Your accept rate is calculated on the fly when you accept or unaccept an answer, either triggers a recalc immediately. We also recalc an accept rate when merging/unmerging user accounts...aside from that the calculation also runs once a day for all users, that's the one you have to wait for when dealing with deleted content.
If you look now you'll see your accept rate is correct, since the nightly sync job has run.