Did Jacob know who he was wrestling with at Peniel?
Yes, Jacob knew who he was wrestling with. Although Scripture does not state it directly, the context implies he understood he was wrestling with the God of his father Isaac and grandfather Abraham, and that unless this God blessed him, he would be destitute.
Les teaches that this was not a figure of speech but a literal theophany: God came down in the form of a man and wrestled with Jacob. Although Scripture does not say directly that Jacob knew who he was wrestling with, Les explains it is clearly implied. Jacob knew he was dealing with the God of his father Isaac and grandfather Abraham, and he understood that unless this God blessed him, he was destitute. This contrasts with Esau, who was destitute of faith and saw nothing in the promises of God. Jacob had a glimpse, just a flicker, that there was something to be gained by getting the birthright as well as the blessing.
And he said, Let me go, for the day breaketh. And he said, I will not let thee go, except thou bless me.
Was Christ literally wrestling with Jacob in Genesis 32?
Yes. The Genesis 32 encounter was a theophany—God the Son appearing in human form—so Christ literally wrestled with Jacob. Jacob recognized he was dealing with the Lord, and he held on, saying he would not let Him go unless He blessed him.
Why did Jacob refuse to let go until God blessed him?
Jacob refused to let go because he recognized he was wrestling with the God of Abraham and Isaac and knew that unless this God blessed him, he was destitute. Having a glimpse of the promises, unlike Esau, he saw the birthright and blessing as something worth gaining.