They can make it easier to remember. For example, if you know the origin of '人' (person) as a simple drawing of a person standing, it sticks in your mind better.
Well, kanji is vital. In light novels, it can enhance the aesthetic appeal. Readers who are familiar with kanji can quickly grasp the intended meaning. Moreover, kanji is often used for names of characters, places, and important items in the story. Without kanji, it would be difficult to create unique and memorable names, and the overall feel of the light novel would be less distinct.
Tatsumi is likely the main character in the story named 'The Push Man'. He might be someone who is involved in a pushing - related job, but we don't have more details without reading the actual stories.
There are several. Kanji for directions like 東 (higashi, 'east'), 西 (nishi, 'west'), 南 (minami,'south') and 北 (kita, 'north') can be used when describing a place or a journey. Kanji for numbers are also common. For example, 一 (ichi, 'one'), 二 (ni, 'two') etc. Also, kanji for colors such as 赤 (aka,'red') and 青 (ao, 'blue') are often found in light novels to describe characters' appearances or the scenery.
Tatsumi would likely react with defiance. He's a brave character and wouldn't easily submit to Esdeath's kidnapping. He might try to fight back right away if he has the chance.
Well, in general fanfiction, Tatsumi is often depicted as brave and kind - hearted. But in lemon fanfiction which we should avoid due to its inappropriate nature, if any such exist, it might distort these characters in an improper way. Mine is usually seen as strong - willed, and in normal fanfiction she has great chemistry with Tatsumi in terms of their personalities.
Not always. Many manga have furigana (small hiragana or katakana above kanji) to help with pronunciation and understanding. Also, some simple manga are written mostly in hiragana and katakana.
Tatsumi might also face opposition from his friends and allies. They would likely be very suspicious of Esdeath and not understand why Tatsumi is falling for her. His friends could try to convince him that she's not good for him, which would put a strain on his relationships with them as well as his new - found feelings for Esdeath.