Yay! Managed to import all the keys now. Had to first do a normal --dumpwallet on the file, then run the --recover command. It probably reads from the text file instead of the wallet.
"The new wallet ./recovered_wallet_1384453446.dat contains the 306 recovered keys"
Which way is the fastest to check the balance?
Do I have to resync the bitcoin program to check balance, or just use the new wallet?
Your wallet will need to do a rescan, but not a resync. As long as your blockchain is already caught up, you won't have to download/synchronize it again. You'll just have to wait for the client to scan through the blockchain that you already have so it can find any unspent outputs associated with those private keys.