Technically it is a sauwastika (the reversed form) not a swastika. Which has many meanings for different cultures, most of which are popular.
That said I doubt jojo added it because he is a student of world cultures, he is probably trying to be edgy and cool by being an ass or something.
#1 not entierly correct. Manji is the japanese term for the symbol. The symbol is used in many cultures and by many different names. Aauwastika is the culturally generic term most often used
#2 Fair, it is used in a lot of places. That is a much better explanation, and its good by me.
#3 Nope
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