Even if you could convince the USCIS that you answered "no" and that you failed to notice that the immigration officer marked "yes" before you signed the document, it would make no difference to your eligibility for the visa waiver program. You are disqualified by virtue of your overstay, and thus (as you were told) will need to seek a visa for future visits.
If you do try to have the USCIS reconsider the question of whether or not you were employed, I suggest working with an immigration lawyer. You don't want the USCIS to determine that your original answer was correct, lest they conclude that you are now committing fraud to try to enter the U.S.

