I find that it doesn’t make much sense to change oil at 4K miles like it suggested in the oil analysis report, of course the metal contents will be lower if you change oil sooner, if you changed oil every day the numbers would be excellent, something is causing the metal contents to go up, the engine is designed to keep the same oil for 10k or a year whichever comes first, in normal duty.
Might be a good idea to switch oil company, would you want to go back to OEM Pennzoil? the aluminum content was also high with Pennzoil, or go to diesel specific engine oil Shell Rotella T6.
The oil samples will be contaminated, specifically if it is taken from the drain plug, even if the engine was just stopped or the sample is taken mid stream. If you were to remove the oil pan from a used engine, gearbox or whatever piece machinery with moving metal parts, you will see deposits stuck to the bottom after draining all the oil, some of those deposits gets sucked out of the drain plug when the sample is taken from there, making the sample contaminated.