"This may sound stupid...because I am not as learned as you both are...but perhaps "Jacob" refers to those that truly belong to Him in heart whereas "Israel" is those that belong to Him in name only...."
Well hmmm, that is so interesting. Jacob could refer to the uncircumcised and Israel to the circumcised. That would be opposite of what you believe. It's like, when Jacob wrestled with God and man, the man could have been himself. He was given the name Israel because he prevailed with God. God is within you.