Decrypt AES-128 with key file but missing IV?
First of all, I suggest you to try use as IV first 16 bytes of encrypted file.
Because in general IV is the first block of ciphertext. 

But if that doesn't work, then – of course – you can decrypt all message except first block. 
Just use first block as IV, and start to decrypt from second block. That will work because CBC does not provide integrity, and you can decrypt parts of the message picking any part of the ciphertext.

To better understand how this works, I also suggest you to read about CBC.