Chapter 20 again shows Abraham's lack of faith in God to protect him by having Sarah say she is his sister, which was a half truth but still wrong. Especially, since he had a promise from God she was going to get pregnant soon and have his son. God had to step in again to fix the mess Abraham had made.
Abraham is the first prophet mentioned in the Bible and it says how he could pray/intercede on one's behalf.
Ishmael mocked Isaac when he was a toddler. Sarah saw it and wasn't happy at all about it. Sarah wanted him and his mother casted out, Abraham was sad about it, but God told him to do as Sarah asked. He did this because the promise of the savior was to be through the offspring of the child God had promised not the one that Abram and Sarai tried to fulfill it with originally. Also as mentioned in the New Testament the offspring needed to come from the free woman not the slave woman.
God didn't turn his back on Ishmael and his mother though. He kept His promise to her to protect them and make him a great nation. God never leaves or forsakes us just because things might not be how you thought or things are rough, God has you and a good plan for you.
Chapter 22 talks about God testing Abraham by telling him to sacrifice Isaac. I think the story really shows how Abraham has grown in his faith/trust in the Lord. As shown in previous chapters Abraham's faith wavered when his life was possibly on the line, yet here he doesn't waver. Some may say well it was the son's life not his own but as a parent there is this built in instinct to protect your child. Verse 8, "Abraham said, 'God will provide for himself the lamb for a burnt offering' " Abraham was speaking out his faith that God would provide, which He did and always will do.