Way over thinking this.
Ride in the middle ring. If you hit a hill and run out of large cogs, shift to the granny. Once you are done with the hill, shift back to the middle ring.
If you need to go faster than possible on the middle ring, change to the big ring.
Try not to use more than a couple of large cogs with the granny - but sometimes **** happens.
Try not to use the smallest cog when in the middle ring - but sometimes **** happens.
Try not to use the largest cogs when in the large ring - but sometimes **** happens.

You will find you'll break these guidelines - rolling terrain, a steep hill with a bit of relief in the middle, etc. You can trust a rear shift more than a front shift so when conditions are poor like steep hills or when you need to pre-shift you might need to break the guidelines.

I very much doubt you bent teeth from cross chaining.