1. Nobody can say whether it is worth it except you and only after you do it.
2. According to the Ministry of Foreign Affairs' web site on visas, student visa applicants must show "(d)ocuments certifying that the person concerned can defray all expenses incurred during the stay in Japan. In cases where the expenses incurred during the stay in Japan are defrayed by another person, documents certifying the income of the person who intends to defray all expenses and documents showing why he or she intends to defray all expenses for the person concerned are required. "
3. You can extend your stay with the proper visa. What did you have in mind?
I am curious about why you have problems adjusting to an American community college.
It would also be interesting to know why you think studying Japanese language in Japan would be easier to adjust to.