Learn Glide by leveling Final Form. It's easier to get away from the Flames by using Quick Run (Wisdom Form's special skill). Second Chance is learned based on level, depending on which path you took. If you took Sword (which I assume you did), you learn it at level 80. If you took the Shield, then it is around level 55. For the Staff, it is near the sixties.

The preferred levels of fighting Sephiroth is 80+ for Sword, 85+ for Magic (as Seph is immune to all Magic except Reflect spells), and 50+ for Defenders. This is the same across all game difficulties (except possibly for Magic, which will likely make you go higher for Proud Mode). This is not just for the Ability Second Chance, but also because your defense rating WILL NOT BE HIGH ENOUGH TO SURVIVE SEPH'S ATTACKS.