I agree that replacing the leather would remove the vintage appeal. How much did you pay for it? Would you be willing to wear it as is? Or perhaps just get the torn leather tabs repaired by a local repair person? Or even have a crafty person embellish your bag?
I definitely think you should make another trip to Louis Vuitton, see a manager who hopefully is a different one than last time, and explain why you believe this bag is authentic and get a second opinion. If they won’t work with you, just pay an authenticator. I hope you get your authentication answer soon.
Sheesh, I really need to proofread before posting so I don’t always have to edit!!