I have to point this out again, but regardless what Contact Harvest and other lines of dialogue that hinted to humans being Forerunners, the Halo 3 Terminals and the Halo 3 Cradle of Life comic contradicted the whole plotline that Humans = Forerunners. While I do agree Contact Harvest contradicts it aswell as 343i's statements before the Forerunner trilogy of novels, the fact is Bungie's own canon contradicts that and supports 343i's canon decisions. Bungie's tier of canon dictated that in-game canon took priority over the novels, therefore with that logic the Halo 3 Terminals > Contact Harvest. If Bungie was so for it, they should have enforced it but instead did the opposite.

Other than that though I agree with alot of your points, though looking at Destiny I can't see Halo being anymore relevant than it is now, at the very least things are improving and hopefully 343i continues to improve.