Is this a reasonable setup for terminating and protecting an RS-485 transciever?
A real RS485 bus would be setup for bidirectional transmission and not dedicated to one way flow. If you want to use unidirectional flow you should be more apt to study termination techniques for RS422.

Symmetrical parallel termination at each end like you show is what you want for a bus that needs to transmit in both directions.

For unidirectional transmission you really only need the 100 ohm termination at the receiver end. You could also choose 50 ohm resistors in each leg at the transmit side which would be optimal termination for a driver.

The 680 ohm resistors are only needed for fail safe termination at a receiver side to bias the receiver to see a "stop bit" voltage level in case a cable is disconnected. In your case they are not needed at your transmitter driver side.