Breaking Dawn Pt 2...when Alice and Jasper mostra up just before the 'big fight'....every one was tense and on edge..why Jasper didnt control everyone's moods and make everyone calm and peaceful?

That could have been an alternate way to avoid a fight, but te have to remember, at that time both Alice and Jasper knew they had the evidence - Nahuel and also Alice's vision in the film version - which'd make the Volturi back down. Jasper didn't calm everyone down and force there to be no fight because there was no need.