The Exodus was over 3,000 years ago. Why bring it up every morning?
Count how often this short prayer says it. Four times in sixteen verses we are told that God took us out of Egypt with a strong hand: three times as bechozek yad, "with strength of hand," and once as beyad chazakah, "with a strong hand." Both of the verses here about tefillin end with it. Whatever else tefillin are, the reason these two passages give for them is Egypt.
Rashi (Rabbi Shlomo Yitzchaki of France, died 1105) reads the words "Remember this day" as a rule: we mention leaving Egypt every day. Not once a year at the Seder. Every day.
Why that often? The Ramban (Rabbi Moshe ben Nachman, who lived in Spain in the 1200s) answers at the end of his comments on this passage, and he is blunt. God does not perform a sign or a wonder in every generation in front of every person who denies Him. So we were commanded to keep a permanent reminder of what our eyes saw, and to hand it to our children, and they to theirs, down to the last generation.
He lists how. Write it on your arm and between your eyes. Write it on your doorposts. Say it out loud morning and evening. He also explains the placement: the written record of leaving Egypt goes on the arm and the head, next to the heart and the brain, which he calls the places where thought lives.
Then the Ramban goes one step further. From the great public miracles, he says, a person comes to admit the hidden ones. He means that everything that happens to us, to a whole people or to one person, is a miracle too, and none of it is just nature running by itself. On his reading, the daily reminder of Egypt is meant to change how you see an ordinary day.
That is the Ramban's explanation, and it is one explanation. The verse itself gives a shorter one: "so that the Torah of Hashem will be in your mouth, because with a strong hand Hashem took you out of Egypt."
Shemot 13:3, 13:9, 13:14, 13:16,Rashi on Shemot 13:3,Ramban on Shemot 13:16Why do firstborns belong to God?
The prayer opens with it: "Make every firstborn holy for Me ... It is Mine." The second paragraph gives the reason, as an answer to a child's question. Pharaoh refused to let us go, and every firstborn in Egypt died. "That is why" firstborn animals are offered and firstborn sons are redeemed.
Rashi (Rabbi Shlomo Yitzchaki of France, died 1105) puts God's claim in one line: I acquired them for Myself by striking the firstborn of Egypt. The Torah says the same thing later, in the book of Bamidbar: "On the day I struck every firstborn in the land of Egypt, I made every firstborn in Israel holy for Me."
Holy for what? Rashi explains that the service of God was first done by the firstborn. When they sinned with the golden calf they were disqualified, and the tribe of Levi, who had not worshipped it, was chosen in their place.
What remains is the redemption. The Torah sets the price at five silver shekels, paid to a kohen once the baby is a month old. It is still done. If you are a firstborn son, it may have been done for you.
The Sefer HaChinukh (a book from Spain in the 1200s that gives a reason for each commandment) gives two reasons. The first would make sense even without Egypt. A person works hard for something, and the first result is the one he loves most, "like the pupil of his eye." He gives exactly that one to God. Doing so teaches him that everything is God's, and that a person has only what God shares out to him. The second is the Torah's: to remember the great miracle God did for us with the firstborn of Egypt.
So there are two reasons on the table. The Torah's own: it goes back to the night the firstborn of Egypt died. And the one the Chinukh puts first: give away the first of what you love, and you will remember where all of it came from.
Shemot 13:2, 13:15,Rashi on Shemot 13:2,Bamidbar 3:13 with Rashi on 3:12,Bamidbar 18:15-16,Sefer HaChinukh 18God killed every firstborn in Egypt. Am I supposed to be fine with that?
You say the line every weekday: "Hashem killed every firstborn in the land of Egypt, from human firstborn to animal firstborn." It is fair to stop on it. The Torah does not soften the sentence.
Start with what the Torah says came before. Pharaoh had commanded all his people: every boy that is born, throw him into the Nile. And before the first plague, God gave Moshe a message for Pharaoh: "Israel is My firstborn son. I told you: let My son go so that he can serve Me. You refused to let him go. I am going to kill your firstborn son." Nine plagues came and went first. The passage you just read says it happened "when Pharaoh was too stubborn to let us go."
Rashi (Rabbi Shlomo Yitzchaki of France, died 1105) asks the hard part of your question outright. Why were the sons of slave women struck? Why the captives? His answers: the slaves also put the Israelites to work and were glad at their pain. The captives were glad too, and had they been spared they would have said their own god brought the plague on Egypt. And the animals? The Egyptians worshipped them.
You may find those answers enough, or you may not. Either way, notice that Rashi does not skip the question.
One more source. When the Egyptian army drowned in the sea, the Gemara says the angels wanted to sing. God stopped them: "The work of My hands is drowning in the sea, and you are singing?" On the same page the Gemara states it as a rule: God does not rejoice when the wicked fall. Then it adds a limit, in the name of Rabbi Elazar: God does not rejoice Himself, but He does cause others to rejoice.
So the question stays partly open. What this Gemara does say is that God Himself takes no joy when the wicked fall, the Egyptians included.
Shemot 13:15,Shemot 1:22,Shemot 4:22-23,Rashi on Shemot 11:5 and 12:29,Megillah 10b