Circuit Protection to the current circuit
In order to protect from overvoltages, a zener is a common solution. They have a 'zener voltage', for 5V buses, 5.6V zener voltage is commonly used.
For avoiding overcurrents, you could use simple fuses, in order to size it you could measure what the current is under normal operation and then use one with a rating, say 30% above that current value. Bad thing about fuses is that once they trip you have to replace them. If you want to avoid that you could use PPTC which are similar to fuses, but once the short circuit is repaired, they turn back to normal, so you don't need to replace them.
Also, you said that you use a diode to avoid reverse conduction. That is definitely a good idea, although the voltage drop in a diode could be significant (up to 1V in some cases, 0.4V if you are using a shottky), in case that this diode created an issuee, a PMOS could be a good idea (with the body diode connected in the same polarity as you have your current diode).