SN65HVD3x (RS485 Driver) - Termination resistor
You don’t misunderstand it as far as I can tell. The load of 40 ohms is a little too heavy for the device in question so, take a look at figure 37 (on the use of protection devices) and note that 10 ohm resistors are inserted in the driver output lines. If you can implement this (with or without the TVS diodes) then it might be a way forward for you.

You should also note that using a terminating resistor that is a little higher in value won’t degrade the signal quality too much. Maybe also consider 100 ohm terminators.