You are not connecting to the right network when starting geth, hence the 0 balance. The --ipcpath just tells geth where to store the IPC file when other local processes want to connect to your node. You need to specify the --testnet option to connect to Ropsten. It looks like you want to use the coinbase account for checking your balance, so you should also pass in your address with the --etherbase option.
alias geth = 'geth --ipcpath /home/tom/.ethereum/testnet/geth.ipc --testnet --etherbase \'YOUR_ADDRESS_HERE\''
You can get the full list of geth commands here.
Once geth starts, you'll also have to wait for your node to sync in order to get your balance.