What point does Equiano make by asking questions at the end of this narrative?

I think that the questions that he asks are rhetorical in nature. We already have the answers after reading his book. Equiano hopes the abolishment of the slave trade will soon be at hand. He spent some time in Ireland in 1793 and then returned to London to hear the debates on the slave trade in April of 1795. That month, he was also married to Miss Cullen, the daughter of James and Ann Cullen.

He concludes his narrative by humbly explaining that there may not be any merit in it, but that the inclusion of each event within was undertaken because they are so vividly impressed upon his mind. He sees how the hand of God is present in every event, and that each of these episodes has taught him to become better and wiser and to "walk humbly before God."