Yes you check Divorced under 17, and if you read 18 it states (Even if divorced or separated.) So you need to fill 18, and 19 with info of your EX.
From Nolo law guide "Fiance & Marriage Visas" states for those lines:
QUOTE
Check any appropriate box except "married" or "separated" You're only supposed to be a fiance at this point, not a married person. If you are separated from a previous spouse, the divorce needs to be finalized before you continue with this application.