One of the main themes is redemption. The protagonist, Rudeus, is trying to atone for his past mistakes in his previous life. Another theme is growth. He constantly develops his skills and matures as a person throughout the story.
Rudeus is quite interesting. His complex personality, with his insecurities from his past life and his growth in the new one, makes him stand out. Eris is also great. Her fiery and headstrong nature adds a lot of drama to the story.
In certain fanfic concepts, Naruto could learn Edo Tensei from Kabuto. Kabuto, having mastered the jutsu, might decide to teach Naruto for some reason. It could be because he sees Naruto's potential to use it in a more positive way compared to how he misused it. Naruto, with his strong sense of justice, would then try to modify the jutsu to be less evil - like not using it to bring back people against their will.
Hard to say. It could be on hiatus, but without concrete information, it's difficult to give a definite answer. Try following the mangaka's social media or the manga's official website for the latest.