Excellent Question
You wrote:
The question is this: Given that the Sun's output has risen by some 30% according to current stellar theory, how has the Earth managed to stay so comfortable?
That is the $64 question (no adjustment for inflation).
Assuming that current stellar theory is valid and that interpretation of the geological record is accurate, then the answer must be that there is some thermostatic control either by Earth itself, or by some other force, body, or agent which has eluded detection, or whose effect is not recognized.
Thanks for posting the informative charts, and for raising this most excellent question.
S