The first question is very complex, I will try to answer it as I see fit. Certainly between ancient Rome and modern Italy (understood as a historical and cultural reality, not as a state), there is a special relationship, but I do not see them as a single thing; Italian culture is the child of different influences, above all, Greco-Roman civilisation and Christianity. To the question of why Dante chose Virgil, the reason was another: So Dante chose Virgil as a guide for his journey through Hell and Purgatory because he considered him a most illustrious poet, a 'master'; even though he placed him in limbo, and therefore knew that he was not a Christian, he considered him a prophet.