Can I stay in China for 6 months if i have a Multiple Entry Visa valid for 6 months?

Validity of 6 months doesn't mean you can stay in China for 6 months continuously. Each entry should have a limited duration of stay and you must travel out of China before that entry is going to expire. Travelling to Hong Kong and Macau is considered as traveling out of China in this situation.

So what would you recommend for me if I'm going to stay there for 6 months?

You should apply for a single-entry business visa (F visa) with 6 months stay duration. Then you don't need to leave China during the study. The student visa is divided into two types: F visa for less than 6 months study, X visa for more than 6 months study.

Please provide the admission letter and JW201/JW202, your passport and the completed visa application form.