Power supply protection (limiting the voltage)
If you really want to protect your sensors, then shorting the output of the Murata DC/DC converter is both the easiest, simplest, and safest way.  If there is an overvoltage condition, then there are capacitors charged to that potential on the output of the power supply, and that energy is either going to into your sensors and destroy them, or it can go partly into your sensors and something else (and still destroy your sensors) or it can be consumed by a dead short so quickly that the over voltage condition doesn't have time to hurt your sensors.  

A buck converter like the one you're using tolerates output shorts very well, and it simply has to not turn on one MOSFET (the top one) to survive a short indefinitely.  Which it certainly will do. Most buck converters with over voltage protection in fact short the output through the synchronous MOSFET until the voltage falls so it is back within regulation, so it's definitely the standard and most reliable way of doing this.

Use a thyristor/SCR crowbar circuit.  It's thousands of times faster than the fastest fast blow fuse there is.  You can use a zener or zener reference like the TL431 to set a very sharp trigger voltage.  The DC/DC converter will quickly shut down as it's overcurrent protection is triggered before any damage comes to your sensors, it, or the crowbar.  

As for negative voltage, put a diode in reverse across the power rails.  If instead the power supply is hooked up backwards, 5V to ground and ground to 5V, the diode will turn on and conduct like a short, which will engage the Murata DC/DC converter's overcurrent protection yet again and hopefully save the sensors.  A fast schottky diode would work best here.