I want to use another wallet.dat file with bitcoin-qt. Is this possible?
You're on the right track -- in fact you're already using the correct command line switch, which is "-rescan".  But your mistake is thinking this is a quick solution.  It's not.  Rescanning the blockchain will take hours, depending on your processor speed.

This is a task you'll want to leave running overnight.  If the problem persists even then, record the error message you get once the rescanning has completed, and ask another question with that error message.

Your next option would probably be to actually transfer the Bitcoins using a tool like pywallet, but I'd wait until you've left this rescanning overnight before you try that, and seek guidance on how to use pywallet.