10 August 2018
Thanks for sharing this more detailed description. ANSYS Maxwell can certainly be used to good effect here. You can use the electric field solver to understand the electric Potential, electric Field distribution, and also the electric Field Stress associated with each spark gap geometry and material. You can use the post processing to understand exactly when the point of dielectic breakdown occurs - It won't be able to model the behavior of the arc itself, but your goal is to understand at which voltage breakdown occurs and the spark gap discharges. So yes I believe Maxwell has you covered.
I located this most excellent Masters Thesis by Karthik Reddy Venna, which looks at the dielectric strength of HV vacuum interupters. Although these devices are a largers scale than PCB spark gaps, the simulations and methods described are directly applicable. Please take a look:
A Simulation Analysis to Improve the Dielectric Strength Inside High Voltage Vacuum Interrupters