How helpful is it for me to have a family member with a green card in America? How high is the English requirement? If you want to go to school there, can you apply?

Having a green card at home doesn't help you at all. The city where you go to college is the same as the place where your family lives. They are willing to provide you with food and accommodation. That's all you can do.

Generally speaking, the gold content of American undergraduate courses is higher than that of graduate students. I suggest that you start to transfer now and continue your undergraduate studies in the United States.

English level depends on which school you want to apply for. Generally speaking, the TOEFL of TOP50 is 1 10+, after 50 it is about 100, and after TOP 100 it is 65- 100.