At the beginning of FL-180 and item 4(a)1, you should enter the date, six months plus 1 day after service. For example, if your ex was served on Jan. 1, you should enter July 1 in both locations.
The date on FL-190 is the date when judgment is entered. The clerk will enter this date. The effective date of change of your marital status is controlled by the date of entry of judgment.
Your tax filing status will be determined by your marital status on Dec. 31.
Most courts have local rules that you must comply. For example, the Nov. 2 deadline. If you want your judgment to be enterred before Dec. 31 you must file the judgment forms before Nov. 2. It was not the court who caused the delay if you missed the deadline.
About the ex parte motion. You can file FL-300 and tell the clerk it is ex parte. An ex parte motion is normally for emergency situations or calendaring issues, without giving your ex the required notice. If you really want a judgment before Dec.31, you may try. Your chance to get an order, however, is slim for a number of reasons. First, it is a default judgment and there is no burning issue that requires immediate court intervention. Second, you were late filing the judgment form, which the court is not responsible for the delay. Third, you may not be able to schedule a hearing date before Dec. 31 anyway. Courts may go lights out during Christmas break. Last, you are doing it for financial gain, which courts normally frown upon and may even order sanctions if the motion is denied.