First, you have a certain school experience and a certain understanding of some university courses, but only 70 points is not high, so you should be prepared to take many courses again, because many courses may not be certified abroad after studying in your country.
Second, your main strengths are math and high school experience. Your college entrance examination score is an attractive figure for any foreign university, and there should be no problem with your IELTS score. I assume that your IELTS level is not too bad, and it should be no problem for the University of Singapore to ask you.
Third, your award-winning experience is more secure. The talents that foreign universities like are not the comprehensive level of your college entrance examination results, but more your professional achievements. You are outstanding in mathematics. Doing research in foreign universities, whether it is computer, economics or other projects, is very popular. In this way, as long as you show your achievements in your personal statement and recommendation, you can get a full reward.
In a word, it is very promising for you to win the full prize of the National University of Singapore, as long as you prepare some more courses.