Yeah, you should always be able to access your private keys with alt+j, after removing the wallet password and restarting, in case you can’t get Bisq to connect properly to the Bitcoin network to publish a transaction.
You should double check your Internet connection if it works fine and confirm that you have enough Bitcoin network peers in Settings->Network Info. If all looks good, you can try deleting the SPV chain file in Settings and restarting the app.
PS: In order to withdraw your funds at any time, you can use cmd+e if your Bisq client can connect to the network without any issues.