Sure. For instance, Hercules is sometimes featured in DC Comics and can be classified as a demi-god. Also, there are other characters with similar attributes and powers that fall into this category.
There's no way to really tell if it's common specifically for someone named Jojo. However, in general, reading fanfiction is a popular activity among fans of many different franchises. The Jojo series has a large and dedicated fan base, so it's likely that there are fans named Jojo who partake in reading fanfiction, but we can't say for sure how common it is without more data.
The chakra powers of Naruto characters could potentially enhance or disrupt the natural powers of demi - titans. For example, a Sharingan - user might be able to predict the movements of a demi - titan better, or a jutsu could be used to temporarily immobilize a demi - titan.
Perhaps this Jojo is interested in exploring different interpretations and stories within the Jojo universe that fans have come up with. Fanfiction often takes the existing characters, settings, etc. from the original Jojo series and creates new and unique storylines. So, this Jojo might be a big fan of the series and wants to see what other fans have imagined.
I'm not sure specifically as there could be many novels related to demi - gods. Generally, it might be about the adventures, powers, and relationships of demi - gods, who are half - divine beings.
It depends. Maybe there are some telltale signs or elements that suggest it's a JoJo reference fanfic, but without specific context, it's hard to say for sure.