The words of the Lord are those from a higher authority. They are commands to be obeyed. Moses's speech would have been incrediblely offensive to Pharaoh and would have taken courage to say to him. The same word produces a radically different response and impact with the Israelites. This is why God's word should not be modified.
Verses 24-26 are difficult to talk on. The "he" it refers to isn't known for certain (majority believe it to be Moses, some think it is Moses firstborn son. God could have been putting Moses close to death for failing to have his son circumcised. Since Moses is being called to be a lawgiver and have others obey God, he should do the same before preaching this message.
Technically, the father is supposed to do the circumcising, but in this case the mother did so. We believe it is because Moses was near death. Doing so, she saved her son's and her husband's lives (this foreshadows the blood sacrifice of the Passover). We aren't sure whose feet are touched or whether her statement was meant to be positive or negative.
When Moses meets Aaron, there is an emphasis on the word "all" (contrast with Moses' previous failure of following all God's commands).
God's people rejoiced and worshipped God even while being enslaved.
Salvation is about sacrifice.