The part is Aluminum and the screw going into it is steel.

The threads wore down due to the part being loose

Steel is harder than aluminum so the screw destroyed the part rattling around in the threads and being pulled when brakes were applied

The heli-coil is steel and secured with red locktite. So now it’s a steel on steel interface and is stronger than before.

Torque wise brake mounts typically require 70-90 inch pounds (7.5 ft pounds on the high end) of torque. (In most cases tight is correct)

Exactly this.

Threaded inserts are an option with more space but bicycle parts are small

As far safety the threads in the part are now stronger than they were originally so it would be reasonably safe to put it back into service.

My kids and I read Harry Potter a lot. We love it and it’s been a good bonding experience.

We limit our consumption of Harry Potter though. We read the books, watch the old movies and occasionally (once a year) maybe, purchase a lego set.

I have explained to my kids that I would rather not support JK Rowling due to her stance on trans people and for the most part they are cool with things.

I am certainly still not helping but I believe my kids understand pretty well