As far as I know, they account for the study abroad if it's part of your degree program. In any case, not sure why you're worried about it as the adcom isn't in the business of recalculating and reformulating GPAs - they simply don't have time to do that. They will basically take a glance over your transcript to get a feel for what your coursework was like and whether taking into account your study abroad will make a .01 or .10 difference in your GPA isn't really what it's about. They're not that granular.
As for taking quant courses, if you can take one or two in your senior year and ace them, by all means go for it. You'll have to do well on the GMAT nonetheless, but if you can get some of the quant work done now to balance out any poor grades you had previously in your quant courses, then do it.
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