He might be shocked. In the fanfic, if he sees things like his friends' future achievements or the new threats that emerge, it would surely startle him. For example, if he discovers that one of his friends has a family of their own and has become a great leader in the village, he would be proud but also a bit surprised at how much has changed.
With his usual determination. Naruto has always been one to face difficulties head - on. So, even if he's shocked by what he sees in the fanfic's future, he'll likely try to find solutions immediately.
Sukuna does die in the manga. The way it happens is quite dramatic and ties in with many other elements of the story, adding depth and tension to the overall narrative.
No. Ryomen Sukuna is a fictional character from Japanese mythology and modern manga/anime. He doesn't have a basis in a true historical event or person.
Nope. Ryomen Sukuna has no basis in reality. It's a product of the creative minds of the writers and illustrators who designed a captivating fictional character for the enjoyment of the audience.