Retake dilemma

Got 2210 in first SAT - 800M, 770W, 640 CR
Second SAT was 2160…- 680M, 720 CR 760 W
Superscore comes at 2290 with Math + CR at 1520
Should I be retaking the SAT?
In case I do retake the SAT, and get worse than current scores, how badly will that impact my admissions chances (if you take the big ones like Stanford and UCB into context)

I was getting consistent 2250-2350 in Blue book before second SAT and am surprised at the math score especially(I’ll be applying for engineering 2017 intake). I am not sure whether I should send second SAT score for hand verification also??

Note: I’m an international student

Edit: I’ve not taken any test after those two. However, I’m reconsidering doing ACT. Problem is that my single-sitting best score is 2210, but reading comes as 640. This proves to be a problem when applying to Berkeley. Even more so when you consider that I’m an international applying for a STEM major.
On the other hand, my senior year course load is tending on the heavier side and I would also be doing 3 subject tests at the same time.

So the question is: Should I take ACT in September/October and try to aim for a 35+(which I believe I’m capable of), or not?

If you’re confident that you can do that well on the ACT, then go for it. A lot of people do significantly better on one test than the other, and I think universities realize this. From what I’ve heard, they really only consider the highest scores even if they ask for all of them. That being said, your SAT scores aren’t bad to start with- a 1520 is just above average for Stanford for instance (I’m aware the old -> new conversion isn’t perfect), but if you can even get a 34+ on the ACT, It’d be better than any of your current single-sitting scores.

Would my chances be increased if get a high ACT score though? Considering that, at least for the top colleges, they look beyond your test scores and more at other parts of application.
Should I try to bump up those other parts rather than doing ACT? Or should I just go for ACT?

Your chances would almost certainly increase if you did well on it, but I can’t really judge if your time would be better spent on studying or on extracurriculars solely based on the information you’ve provided. You did say that you’re studying for practice tests though- if you can score really well on those, it would support your academic strengths enough that you’ll be fine as far as testing goes. Since you’re applying to schools that require all tests to be submitted, why are you studying for three SAT II’s? If you can get 780+ on Math II and a science, you’ll meet the required two subject tests for most schools (I’m assuming you’re not applying to Georgetown). If you do that, you’ll have more time to focus on your extracurriculars, and still have average to above average test scores.
That’s the best I can recommend with the given information- if you’re willing to tell me more about your GPA, class standing, outside interests, specific schools, etc., then I could probably give you a more specific answer.