Yes, your understand is correct. The maximum current consumption of FX3 is about 260mA.
You can take more than 500mA current as long as your design meet the PD Spec.
You can also choose other OVP chip which can take more than 600mA, because it's better to monitor the OVP event of entire board not only CX3.
Thanks! Do you have a recommendation for another OVP with let's say up to 1-1.5A support?