Hinata would be heartbroken at first. Naruto is someone she deeply cares about. But she's also a strong - willed ninja. So she might start by trying to understand why Naruto left. She could look for clues in the village or talk to Naruto's friends to figure out his possible destination.
Hinata would likely go to great lengths to save Naruto. She might seek help from the most powerful medical ninjas in the village or even venture out to find a rare herb or a mysterious healer. She would be in a state of shock at first, but then her love for Naruto would drive her to take action.
In some fanfictions, Naruto is completely oblivious at first. He doesn't understand why Hinata is acting strange. He just goes about his day, being friendly as usual. But as Hinata's jealousy becomes more obvious, he might start to notice that something is wrong. He could be confused and try to ask Hinata what's bothering her.
Hinata might be shocked at first. She is a gentle soul, so seeing Naruto be so violent towards Sasuke would be unexpected. But then she would probably try to stop Naruto, as she doesn't like to see people fighting. She might also feel a bit guilty, thinking that her relationship with Naruto somehow caused this conflict between the two friends.
Shikamaru, being the more laid - back but perceptive friend, would likely be disappointed. He might see the signs that led to the divorce coming from a mile away but feel powerless to stop it. He would probably just sigh and say something like 'What a drag' while still being there for both Naruto and Hinata as a friend.
Sakura would be really happy for them. She has seen Naruto grow and has always wanted him to find true love. Since she has moved on from her old feelings for Naruto, she would be supportive and might even offer to help with the wedding preparations. Shikamaru would probably be a bit lazy about it at first, but deep down he'd be glad for Naruto. He'd say something like 'What a drag, but if it makes you happy, Naruto.' Kiba would be excited, especially since Hinata is his teammate. He might tease Naruto a bit about finally getting the girl.
Kiba would probably be shocked. He's Naruto's friend and also has a connection to Hinata. He might try to convince them to stay, saying things like Konoha needs them. But once he realizes they are determined, he would support them in his own way, like promising to visit them. As for Lee, he would see it as a very brave decision. He would be inspired by their courage to step out of their comfort zone and start a new life elsewhere.
Their friends would be overjoyed. Sakura would probably be really excited and offer to help Hinata with any medical advice during the pregnancy. Shikamaru might give Naruto some practical advice on how to handle the added responsibilities. Kiba could be really happy and joke around about the new baby being a future ninja partner for his own pups. And Ino would be eager to plan a baby shower for Hinata, full of beautiful flowers and gifts.
I'm not sure if there is such a fanfic. Cheating storylines in fanfics can be quite controversial as they go against the positive relationship often depicted between Naruto and Hinata in the original work.
His friends would be really happy. Shikamaru would probably be like 'Well, it was bound to happen eventually, Naruto.' and offer some practical advice. Choji might bring over some delicious food for Hinata to help with her pregnancy cravings. Kiba would probably joke around with Naruto about how his life is really changing now.