As a fellow introvert, I totally understand the extreme discomfort you must have felt in a customer-service position! Talking to people all day long (especially people who may be frustrated or upset) is incredibly draining for a true introvert. So I can see why going back to that position isn’t ideal for you! But I would absolutely try asking for a raise, using the recommendations in the Muse article (glad you found it helpful! 🙂 ).
I’m curious — have you looked into doing voice-overs as a full-time job? I know you don’t want a side job in addition to your full-time job (as a Thriver, that’s not going to fit with your values), but I imagine there must be full-time positions doing voice-overs. And you could possibly do it remotely, too, if you had the right equipment. Something to look into!