A few thoughts.
How to explain to law schools why you went to 3 different colleges, if you could even get into one as good as Amherst at this point?
You don’t have to take math to graduate form Amherst, you may have to if you transfer. I am not familiar with the LSAT but does it have math on it?
Ugh, this attitude makes me think you won’t be happy anywhere. Smith, MoHo, Hampshire and Umass are all great schools with terrific classes that you can explore easily and for free. If you hate being on Amherst campus, then take as many off of it as you can.
Think hard about what you can do now to make your current school work. How about going abroad for ALL of junior year, not just a semester? That gets you halfway there. And you don’t have to leave the country if you don’t want to, you can spend a year on another campus in the US - without having to go through the apply/transfer process. You’ll keep your financial aid, if that is important.
Pretty much any US university that accepts visiting students is available to you: https://www.amherst.edu/academiclife/global-learning/study_abroad/new-resources-for-students/program_list