Interesting. Climate here is not as extreme as AZ summers, but just went from 5x30 to 10w30 due to mileage over 100k in one vehicle. Using Mobil semi synthetic. I never go over 3500 for oil changes, and I always keep it near the top mark on the stick. The more oil the more heat dispersion.
Also when I change oil/filer I let it drain for 3 hours. Unlike the local jackball lube places. They always leave about a a 1/4 quart of dirty oil in the engine. At start up I fill the filter half full of oil then screw it on so the motor has oil where it’s needed fast at start up.
You have a good plan. As you stated I found a dark ting in my oil following oil changes performed by various service organizations. So I decided to go the DIY route. I drained the pan dry, replaced the plug, and pulled the filter. While the filter area was drainied dry, I filled the new filter up with oil. This takes a few tries. Installed it. Filled the crankcase with top flight new oil and voila I still had a dark tinge. Hmmmm... The hotrodder in me was irritated. The next time I changed oil, after I installed the new filter, I pulled the pan plug a second time and found an additional quarter to half quart of old oil. I believe the upper oil galleries and, in my case, the displacement on demand manifold, vacuum locks until the oil filter is removed. Some of this oil drains to the oil pan while the majority drains through the oil filter adapter. After that clean oil on the dipstick! Much joy!! But, it takes three to four hours to drain the engine properly.