Hello James, I would not agree with that Minnesota congressman’s statement regarding Jefferson’s Qur’an or his views regarding the religion itself. One cannot draw that kind of conclusion based on the fact that Jefferson owned a Qur’an. I myself own one as well as the apocrypha of the church such as the gospel of Thomas. I also own the Talmud and a traditional Protestant Bible. The mere owning of a book does not mean an endorsement of that religion or topic within that book.
You could start looking http://founders.archives.gov/ for your answers. They have many writings and letters from most of the founders.