Earliest U/S showing due date of Aug 29; LMP (irregular) Aug 24. Would this likely be from sex on Nov 22 or Dec 5?

Dec 5. It would be Dec 5 if your dating ultrasound was in the first trimester. If your dating ultrasound was in the second trimester or later, it could be either date.
Dec 5. If the due date is August 24, then the pregnancy resulted from sex on Dec 5 rather than Nov 22.