Good evening Robert,
I can replace that PTC with 0R 0805 resistor if i have trouble in the application.
I'm not sure too but i need to protect against short circuit fail or wrong power supply connection.
I've asked to Microchip about OVP for that IC battery charger but they say only "do not violate the max rating" ... and we know, this is a too generic expression
For the choice i've used exactly the PDF from Littlefuse that you have posted above, i need 30kV! But i've never used before the SP0502B.
I'm trying to design in the best way in order to leave open different ways to make and pass all the test.
Actually i'm planning to design the whole PCB board only with TH and with clearance and components placement/choose for the lowest cost and time
for PCB production and assembly.
Anyway thanks a lot!