TD,
What I conclude( and I could be wrong) when reading wt literature compared to Nu 33:3 is that the Jews began to leave Egypt on Passover day Nisan 14 —that’s why it’s called Passover—but they left in stages as verses 1-5 show. Although they departed from Ramses on Nisan 15 later on, the Passover already began on Passover day after Passover (the meal on the evening prior). WT commentary also notes that there is dispute between Jewish groups such as Caraites and Rabbinical and the Samaritans whether or not Passover meal is on the beginning or end of Nisan 14 and cites Ibn Ezra supporting Nisan 14 beginning. But the fact that Jesus celebrated the passover at the beginning of the day of Nisan 14 validates to JW that it is not on Nisan 14 end with Nisan 15 the following daylight morning as you imply is when the Exodus began.