It is now the 22th day that the tx isn't confirmed. How can I import the private key to another service so that I can spend those coins again?
If Bitcoin Core (aka bitcoin-qt) isn't an option for you, e.g. too long to download and sync, consider using a simplified client like Multibit or Electrum. In the blockchain.info wallet, you can go to My Wallet > Import/Export and the choose export (encrypted or unencrypted depends on your personal context and preferences). Then import the private key according to the instructions of your target client.
You can ask for more specific help if you're stuck. By the way, did you try to contact blockchain.info about the issue? It seems unusual that such a transaction keeps being broadcasted over and over again without ever timing out.
Because I just want to save the money (10000 satoshi in a 0.01 BTC transaction is a quite high percentage) in the fees and I had previously done this with no problem (it confirms within a day). But why this time I can't
Consider consolidating your transactions using multiple outputs (i.e. one payment for multiple persons) if you have many small amounts to transfer and what to save on mining fees.
