I'm confident in saying it's impossible to clear the entire episode as level 1 Lightning. You can definitely kill Caius at level 1 but if you take too long you won't be able to fight Chaos Bahamut. Level 3 makes Caius a joke thanks to CON's Mighty Guard, but it puts you on even ground vs Chaos Bahamut. Level 5 gives you an edge thanks to Aura (HASTE @_@) and I got five stars that way and I didn't even play perfectly.
I'd say 30 minutes overall to complete this episode, but this is pretty much the best battle in the entire game due to it's battle design and needed level of skill from the player.
As for Snow, once he gets to 200% Power you have to let the person he's whailing on die, and then he'll do his "Time to Chill" ability which sets him back to 100%.
EDIT: Putting Spoiler tags since it's about the Lightning DLC ending.
Spoiler: show
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