The part where Harry felt at home at Mac's from the first time he set foot there struck me as similar to his bit of prescient intuition when on Demonreach during small favor. Considering all the roles it plays in his life that you point out, and all the time he spends there between books thats not too unreasonable of a watsonian explanation.

I doubt that mac is going to be the white god or christ though: too much controversy.