Tchaikovsky, one of Russia’s greatest musical geniuses, was prone to bouts of self-doubt and reflection, but with his sixth and final symphony he knew he had a masterpiece on his hands. The “Pathétique” (“Passionate Symphony”) is an abstract exploration of the depth of human feeling and the centerpiece of the Fort Worth Symphony Orchestra’s celebratory opening weekend with Music Director Robert Spano and star violinist James Ehnes performing Sibelius’ glacial Violin Concerto with its “polonaise for polar bears” and Berlioz’s swashbuckling Roman Carnival Overture.