MATLAB: Managing with tolerances in optimization problem(1), setting quadruple precision(2)

optimizationprecisiontolerance

Hi )
(1) i'm using gamultiobj, and fminimax. Could u please tell me how to manage with tolerances, making them consistent and optimal both? Is there a way to get estimations for them without performing a plenty of numerical experiments? If not, could u tell me, what experiments should i start with?
(2) Don't u know how to set quadruple precision for matlab arithmetics?
Thanks in advance )