Naruto would be devastated. He might blame himself for not being able to protect his son. Sasuke would be angry and would likely go on a hunt for the perpetrator. His friends like Sarada and Mitsuki would be heartbroken. Sarada might vow to become stronger to prevent such a tragedy from happening again.
First, do your research on the otsutsuki. Know their powers, their appearance, and their general behavior in the original source material. This will help you create a more believable story.
Well, his pure Otsutsuki blood might enhance his physical strength. For example, he could have greater stamina and be more resilient in battles. His dojutsu abilities could also be amplified. Maybe he can use the Sharingan or Byakugan in a more powerful way than normal. He might also have a natural affinity for Otsutsuki - related jutsu, like those involving space - time manipulation.
Boruto's reaction would be complex. He'd be heartbroken, for sure. He might start to question his own worth and purpose. But over time, he'd realize that he has to carry on Naruto's legacy. He'd become more serious and focused. He'd also become more empathetic towards others, understanding the weight of sacrifice. He might even start to study Naruto's techniques and leadership style more closely, trying to emulate the things that made Naruto such a great Hokage and hero.
Well, as of now, it's hard to say exactly how long the Boruto manga will be. It all depends on the author's plans and the story's development. But it's been building up a significant amount of content over time.
Boruto's strength in the manga is considerable. He's developed new jutsus and strategies, and has overcome many tough challenges. His potential keeps increasing as the story progresses.