No. "Commander" isn't a creature type any more than "nontoken" or "attacking" is.
I know the Protector isn't supposed to pump creatures that aren't commanders, but the way they worded it makes it sound otherwise. Imagine if the word "commander" WAS replaced with "non-token" or "attacking"... I don't know, it just sounds weird. I would've preferred if they worded it "Creatures that are commanders have/get yada yada yada". /my2cents
What about a clone of a Commander or an opponents Commander that is under your control? My assumption is yes on the second but what if it is a copy of an opponents Commander that is in your deck? Is a Commander tracked as a specific card object in any zone or just by name?
No.
Several cards have used "Attacking creatures" in the past in exactly this way.
Berserkers' Onslaught Bow of Nylea Hydrolash