There is no way to lock settings. I too accidentally changed the calibration of the tuner. Since that happened, I just learned that I need to be mindful of the values that are there. You can make a checklist for yourself of what to do.
I made a video of various other tricks that may help you with playing live.
https://youtu.be/o0S6WNKXQKc?si=QO_5CCgPRhhGnE20
As for locking the knobs, you can literally tape them all down with some tape. Or take a piece of rubber and glue it to the Helix so that it touches all the knobs, but lets them be turned. Or find something online, like this thing:
https://www.gearbyceba.com/line6-family-usa/p/helix-floorlt-rack-knob-protectors-short-for-use-with-gearbyceba-full-screen-guards
Honestly, for me, the knobs are not a problem anymore, because I simply learned to double-check this stuff before I start playing.