Primer showing at 220 is a pretty normal thing to catch, lots of guys just shoot over it and never notice until the edge lifts a year later. The 6 hours of block sanding story sounds like the usual old timer tall tale, but the fix itself was solid. Did he actually explain why the edge was showing or did he just point at it and walk off?

The timing of the root work probably mattered more than the work itself. Silver maples are water hogs, so the deep water schedule kept it alive while the cut roots healed, and most folks skip that part. Your red oak needs the same root flare fix but way less water, so don't copy that schedule or you'll drown it.

That part about everyone hired in the last 2 years making more is the real kicker. It means the company KNOWS what the job is worth, they just set the band higher when they got desperate to fill spots. I have seen this play out where a new hire comes in at the top of the range and the person training them is sitting $10k below the bottom. Loyalty gets punished and job hopping gets rewarded, plain and simple. So next time you talk money, bring up that sheet and ask them to bump you to at least the middle, because staying quiet means you keep funding the new hires.