The relationship of the Haftorah to this week is because it is the Shabbos before Pesach. Just as the nation was redeemed from Mitzrayim 3310 years ago, so too will Eliyahu Hanavi herald the coming of Mashiach.
Pasuk 22 underscores the basis for all prophets and prophesies. The only true Navi is the one who “remembers the Torah of Moshe, Hashem’s servant”. Any Navi that contradicts Moshe’s Torah is by definition a “false prophet”. Many false mashiach’s have arisen throughout history. The only true Mashiach will be the one heralded by Eliyahu himself (a Kohain, by the way)as he proclaims the “coming of the great and awesome day of G-d”.
This week is also known as Shabbos HaGadol – the great Shabbos. Traditionally the Rav of the Shul delivers an afternoon drasha that is intended to review the laws of Pesach as well as inspire the community to ready themselves for the Yom Tov. The custom is to read the first part of the Hagadah in preparation for fulfilling the Mitzvah of relating the story of the Exodus.
There are a number of reasons why this Shabbos is called the “Great Shabbos”. Chronologically, the 15th of Nissan in the year 2448 occurred on Thursday. Erev Pesach, the 14th of Nissan, when the Bnai Yisroel did the 1st Korban Pesach, was Wednesday. That 1st Korban Pesach required that each household take their sheep 4 days beforehand, on the 10th of Nissan, and tie it to their bedposts. Being that the 1st Mitzvah given to the nation was the Korban Pesach, that Shabbos was the moment when the nation performed the 1st step of the 1st Mitzvah given to the nation! Four days before Wednesday is Shabbos. Therefore, the Shabbos before Pesach is called Shabbos Hagadol – the Great Shabbos – the Shabbos when the Bnai Yisroel began their first Mitzvah as a nation.