God frequently bypasses the firstborn, selecting for His purposes another sibling. Jacob selected Joseph's second son, Ephraim, to receive the blessing.
The identical actions of the Lord and the Angel of the Lord show they are the same Being. The God known by Abraham, Isaac, Jacob, and Moses was Jesus Christ.
God is the only perfect example of fatherhood. We need to emulate His virtues, among them being the perfect example of what we want our children to be.