I am totally confused by your scenario. The reason for the cancellation of the flight does not matter as far a refunding your fare if you choose not take a later flight. Southwest owes you a refund, period.

Whether you get compensation for your rental car absolutely depends on the reason for their cancellation.

If they are only offering you the $5.60 refund, that says to me that you booked with points which will automatically put back into your account.