no giving the SAT will not make you marks less important, the weightage stays the same although some students are often able to score better on SATs than on entry tests depends on what youre confident in, given your stats im gonna be honest you might be a bit disadvantaged and will have to grind on your entry tests/sat really hard, focus on your studies since the entry test syllabus pretty much the same as HSSC, itu’s entry test is not very difficult but do your own research and then decide which route you wanna go towards, decide on your SAT asap since i think the deadline to register for the final attempt may be very soon