Sputtered Pyrex films being so thin can breakdown more easily at high voltages
than thicker substrates.  I have use 3.5 MV/m as a safe limit to calculate the
voltage for anodic bonding.  In this case 7 volts should be sufficient for your
application, or a greatly reduced voltage versus 120V.  I have also found that
such thin films do not require much heating.  I would suggest performing the
bond at temperatures closer to 100*C than 350*C.  You can try this on silicon
substrates and use IR to inspect bond interface to set up your process.

Loren St. Clair