Oh Wow, that's a lot of Teflon, you had some fun there!
I see you've used a reed switch for the power too.
A few points I can see:
- You seem to have the protection resistor directly in series with the input terminal, rather than between the 1G feedback resistor and the opamp input / capacitor junction. This will raise the input resistance of the circuits to 10M ohm, rather than acting as a virtual ground (the input should try to stay at ground potential for maximum accuracy). The protection resistor should be inside the feedback loop for maximum accuracy.
- I can't see where the case is grounded to the Green ground terminal, to form a proper screen.
- Ideally, you would air-wire the junctions between the op-amp input, and the input end of the 1G feedback resistor, the 10M protection resistor and the polystyrene cap through to the input terminal. Teflon (PTFE) is good, air is better.
- The most critical leakage path (weakest link) is on the LMC662 package. This needs to be as clean as possible. I think I see some flux residues, not critical as long as the package itself is clean (IPA is best) between the pins.
The great, and much missed, Bob Pease wrote some interesting stuff on the use of Teflon in high impedance circuits, charge storage etc....
https://www.electronicdesign.com/technologies/test-measurement/article/21773611/whats-all-this-teflon-stuff-anyhowand one of his fun videos...
It will be good to see your results. Note that it will probably take a while to settle - leave it with the lid off in a warm dry place, superglue vapours can settle on surfaces (the fingerprint trick in Beverly Hills Cop 2).
P.S. A small hole for trimming the pot won't make any difference to the screening - you can always put an adhesive label over it to keep dust out.