No need to apologize on the grounding thing. We all make mistakes. It's part of learning.
As for changing voltage levels, look back at your table of test results in the first post. If you want the indicator to show full, the most resistance you can have in the circuit is 10ohm.
I'm not sure why you need to, but if you want to increase the control voltage for any given display level, you could put a resistive voltage divider between your voltage source and the op amp input.
