I’d recommend that you read a lot of good books for pleasure, do the best that you can in all your classes in school, do creative writing and poetry for pleasure and submit them for publication in journals that accept submissions from high school students, and if it’s possible, take a college level English lit class while in high school. A 750 on the SAT English is fine - it’s high enough that it would not keep you out of any school that wanted you for other reasons, and an 800 in English would not make you much more attractive to any school that wanted you.
Are you a US citizen, or a US permanent resident? Is your family able to pay for college in the US for you? If the answer to these questions is no, please understand that the odds of getting admitted in the US with a lot of funding are low for you. Make sure that you plan for options for college in India, too.
If you are a US citizen/permanent resident, and are finding the curriculum in your school in India to be focused on memorization rather than analytic thinking, is it too late to change schools? Is there an American or British type school where you live?
Yes, you can submit a writing supplement with your applications. Make it short. Music supplements are supposed to be about 3 minutes long - so figure on submitting something that takes no more than 5 minutes to read, preferably 3 minutes.