I just had a friend who just finished law school who read my said that my 2 pages, while very good and compelling, were excessive in length. Every law student/lawyer i talk to always says "tighten" your language, and says the advice is universal. So I'd say go back and cut any unnecessary or repetitive language, but that's having not even read any of what you've written, so take it with a grain of salt.
But others are correct, depending on what schools you apply to, at 3 pages it is beyond their guidelines.
As far as playing with margins, I'd say small changes are fine as long as they remain in the "printable margins" assuming the school hasn't specified margins already for you (I know Harvard did on last yrs app).