Answer: Your questions are very insightful and may appear at first glance to be impossible to resolve. But with Yahuwah all things are possible, especially in accordance with His word. We must have confidence that He want nothing more than for us to have full understanding of even difficult passages.
At first glance it does appear that Numbers 33:2-4 is speaking of the Sabbath. The sacred hours of the Sabbath do occur on the calendar date of the15th of Abib. However, the sacred hours are the daylight portion only of the 15th. The night portion of this calendar date is not sacred or holy. To discover truth, all of the Scriptures, (Exodus 12:31; Numbers 33:2-4 and Deuteronomy 16:1; Exodus 12:42) must be in harmony. This image below identifies the portion of full calendar date that includes the Sabbath. The Israelites were led by Yahuwah out of Egypt by night after the sacred hours of the Sabbath were over. Refer to article, “When Does a Day Begin?”
A very important command was given the by Yahuwah to all of Israel. Exodus 12:22 states, “None shall go out of the door of his house until morning on the 15th.” Because of this command of Yahuwah, it was an impossibility that He would have led Israel out on the night of the 14th. In fact because of this very command, Moses and Aaron no doubt did not even go to Pharaoh that night as he requested, but would have been faithful to Yahuwah, choosing rather to see Pharaoh after sunrise.
Therefore the only option for the intended meaning of Exodus 12:42 is that all provision of heaven was made for Israel’s release from bondage, on the night of the 14th. While they were in affect set free on the 14th, Yahuwah did not actually lead them out until the Sabbath hours were over, on the night of the 15th.
Further: They also 'spoiled / plundered / looted' the Egyptians – how could that have taken place BEFORE Pharaoh gave Moses permission or orders to leave? So when did the ‘looting’ take place? --- The Egyptians would have been very busy burying their dead during the daylight hours of the 15th - so they were most likely 'looted' after the Sabbath hours ended at dusk, and before the Israelites departed that night.
And the children of Israel did according to the word of Moses; and they borrowed of the Egyptians jewels of silver, and jewels of gold, and raiment: And Yahuwah gave the people favour in the sight of the Egyptians, so that they lent unto them such things as they required. And they spoiled the Egyptians. (Exodus 12:35,36)
Blessings to you as you continue on to know the truth!