Boruto might be in awe. He has always known his father as the Hokage, a powerful and respected figure. Seeing Naruto's past full of struggles, loneliness, and determination would make him realize how far his father has come. It could also make Boruto more empathetic towards Naruto and perhaps inspire him to be more like his father in some ways.
Well, Naruto would be in a really tough spot. He loves his family and the village, and this situation would be a huge blow to his traditional values. He might struggle to understand how this happened between his son and Hinata. Hinata's family, on the other hand, would be protective of her. Her father would want to ensure that Boruto is taking responsibility. Boruto's friends would also be surprised. Some might be supportive, like Shikadai, who would try to see the good in the situation, while others might distance themselves at first, not sure how to handle this new and rather strange development.
Naruto would likely be excited. He loves his son so much that seeing different stories about Boruto would be like seeing different potential futures for him. He might even get some inspiration from the fanfiction to give Boruto some advice in real life.
Well, often in these fanfictions, Boruto watching the past can lead to him learning about the great battles that his predecessors fought. He may witness the Fourth Great Ninja War and see the heroic deeds of his father and the other ninja. This could either make him feel pressured to live up to their legacies or give him the motivation to carve out his own path in the ninja world, different from what has been done before.
The villagers would likely be in shock. Naruto is a beloved figure, but killing his own son would be a very controversial act. Some might turn against Naruto, believing he has gone too far. Others might understand his reasons if they knew the full story, but still struggle with the morality of it.
One of the most shocking revelations could be Naruto's early days as an outcast. Boruto, who has always known his father as a respected figure, would be surprised to learn that Naruto was once shunned by the village. Another could be the danger Naruto faced as a young ninja, like fighting against the Akatsuki. It's so different from Boruto's relatively more sheltered life in the beginning.