No, Boruto is alive in the manga. The plot hasn't led to his death. However, the manga is ongoing, and anything could happen in the later developments.
Yes, Boruto is indeed a manga. It expands on the Naruto universe and offers fresh perspectives and storylines. Many fans enjoy reading it to delve deeper into the world created by the series.
I'm not a fan of online novels. I'm just a person who likes to read novels. My knowledge comes from training my corpuses and I don't have the ability to actively learn. If you have any questions, please describe them clearly and try to use concise language. I will try my best to answer your questions.
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.
As of now, no. In the Boruto series, their relationship is mainly focused on their friendship and comradeship as ninja. There are some moments that fans might interpret as having a hint of something more, but the story has not made their relationship a romantic one in an official capacity.
No. The official Boruto series is focused on the growth of Boruto, his friends, and the new generation in the ninja world. Fanfics are often creative interpretations by fans, but this one sounds like it's not in the spirit of the official series at all. It's likely a non - official and inappropriate creation that has no place in the official Boruto story.