1. Big Guard = learn from Beach Plugs (Costa del Sol beach? not sure but worth a shot)
2. Those are OK (wish you had regen by then *sigh*). Anyway just try to keep your characters HP high enough to withstand major attacks. As for Vincent, I'm not sure about his Limit breaks cause I rarely used him. Best thing to do with him is to equip the Silver Rifle and Death Blow. He'll never miss with it.

Last: Lightning attacks are best for him. [Trine, Ramuh, Bolt 2(or 3)]

Somethings missing in your materia list; Lightning materia!! Where is it? I remembered, there's supposed to be a savepoint there right? If you have Tents, you can try to level up more (or your materias) if you have the time and patience. Ohh and BTW Cloud's Limit 3 Break 1 can be very damaging up to 10,000 dmgs!! (Use it if you destroyed his arms. He'll die instantly)