JMH,
I just want to add a bit more of a response to your question #1.
I have my engine monitor set to give me a "yellow warning" at 400 degrees F on the cylinder head temps, and "red" at 420 degrees F. The reason I did this, is that for my aircraft (NA engine), those temperatures will ensure I have the correct mixture and that I am not doing damage to my cylinders. See also this article from John Deacon
https://www.avweb.com/features_old/p...mixture-magic/ ).
Sometimes, in the heat of the summer here in Texas, I may hit 400 degrees CHT on a cylinder or two on the ground, after run-up. to get cool them off, (if this happens), I ensure I am into wind (if possible) and idle the rear engine and run the front engine up for a bit to get airflow to the rear - and this brings it down should this happen. As long as I do my run-up into wind and do the rear engine first, I have almost eliminated this event.
On Take-off, my cylinder head temps do not normally exceed 340 degrees F - I have spent a lot of time ensuring my fuel pumps are set up correctly, and I run at the top end of the fuel flow when I set them up. I rarely see cylinders going above 360 degrees in the climb for the warmest one, coolest one is around 330 degrees. In cruise, I am always closing the cowl flaps. Warmest cylinder I have experienced in cruise, leaned out, is 384 degrees.
I hope this helps give some perspective. There are a lot of opinions out there, different techniques to run your engines, and even engines having their own personality. Read the articles I indicate will really give you some understanding and help you determine how you want to run your engines.
Have fun with the new engine monitor!
Jeff