Erratic capacitive touch sensor values

If you want physical touch, then don't use capacitive sensing.
Just use a digital input pin to detect mains hum from your body (assuming you're near mains AC).

10Megohm resistor from a digital input pin to ground,
with a 1Megohm resistor between pin and copper strip (for some ESD protection).

Read the pin. It will be LOW without touch, and have a 50 (60) Hz pulse when touched.
Leo..