If the version of Bitcoin Core that you are running is older than version 10.0, then upgrade to version 10.0 or higher.

Then shut down Bitcoin Core.

Open a command line window in your operating system.

Run the bitcoin program from the command line adding -zapwallettxes as a command line option

The wallet will purge all three of these transactions, and will re-scan the blockchain to make sure that it isn't missing any confirmed transactions.

When the re-scan is complete, you will have access to the full balance again.  Resend your 3 transactions, but make sure that you set a proper transaction fee this time so the transactions will confirm quickly.  I always use a transaction fee of at least 0.0001 BTC per transaction, and higher if the transaction uses a lot of inputs or sends to a lot of outputs.