Chapters 11 & 12

Chapter 11 is the warning to Pharaoh of what is to come because he has not let the people of Israel go. God will go throughout Egypt and kill the firstborn son of every Egyptian from Pharaoh to slave and of every animal.
God hardened Pharaoh’s heart (that phrase is pretty common throughout this series of chapters) and blamed Pharaoh for not letting the Israelites go. That to me is a moral monster, honestly. I’ve gone on about it enough, so I’ll be quiet now.
Chapter 12 starts off with a paragraph and a half about how to pick a lamb, use its blood to mark the door posts, prepare the lamb, and eat the lamb. Basically, each household will eat their lamb in one night, leaving none for morning.
The blood is a signal to God that his people live in that house because he is going to go throughout the land of Egypt and kill the firstborn of Egypt. He also gives Moses and Aaron the rest of the instructions for the Passover. On the first day, all yeast (leavening) is to be removed from their homes and they are only to eat unleavened bread for the seven days of the observance. This is followed by Moses explaining all of it to the Israelites.
So God did exactly as he said he would do. He went throughout Egypt and killed the firstborn Pharaoh’s son because he’s creeping death, apparently (Metallica reference). He also killed everyone’s firstborn and everything’s firstborn, because it’s the cattle’s fault if they didn’t know to put lamb’s blood on their stable doors. I do wonder if the sheep and goats were spared since they likely already lost their firstborn to the Israelites.
Finally for the third time in Exodus, Pharaoh tells Moses and Aaron to take the Israelites and leave. This time, God doesn’t harden his heart and instead, makes the Egyptians see favor in the Israelites which allows the Israelites to plunder them. Then the Israelites went from Rameses to Succoth on foot carrying unleavened bread, and taking they livestock with them.
Finally, God gives Moses the instructions for Passover. A lot of this involves circumcision of slaves if they are to eat of the feast. Also, any alien who wants to eat the feast must also be circumcised.
Chapter 13

God tells Moses to consecrate to him all of the firstborn of the Israelites and their animals (more on that later). As it turns out he’s not all about the human sacrifice.
We then get more about unleavened bread because I guess God doesn’t like yeast or something. I do know that there is a lot more about this in the Talmud, but I’m not reading it. However, I have no problem looking for further explanation wherever I can find it. The Oxford commentary isn’t much help here.
We come to the explanation of the consecration of the firstborn, and instead of sacrificing the firstborn of the Israelite people, they will be redeemed.
15When Pharaoh stubbornly refused to let us go, the LORD killed all the firstborn in the land of Egypt, from human firstborn to the firstborn of animals. Therefore I sacrifice to the LORD every male that first opens the womb, but every firstborn of my sons I redeem.’
Bibles, Harper . NRSV Bible with the Apocrypha (p. 156). Zondervan. Kindle Edition.

I’m not saying a word about Pharaoh and his hardened heart…
OK, so God led the Israelites out of Egypt, but not through the land of the Philistines because he didn’t want them to experience war or else they might return to Egypt. Instead he led them to the Red Sea. Egypt was preparing for battle (I assume with the Israelites despite having their hearts softened so that they would help them out). Moses was carrying the bones of Joseph (oh, right, I forgot about that) because he made them promise to bury him with this father when God led them out of Egypt. God led the Israelites as a pillar of clouds by day and a pillar of fire by night.