1a. As per the definition of Enhancement Bonus
An enhancement bonus represents an increase in the sturdiness and/or effectiveness of armor or natural armor, or the effectiveness of a weapon, or a general bonus to an ability score. Multiple enhancement bonuses on the same object (in the case of armor and weapons), creature (in the case of natural armor), or ability score do not stack. Only the highest enhancement bonus applies. Since enhancement bonuses to armor or natural armor effectively increase the armor or natural armor's bonus to AC, they don't apply against touch attacks.
So no, by strict RAW it isn't automatically magical.
Comparing the wording of Metaphysical Claw to the wording of its closest counterparts in spells (Magic Fang, Magic Weapon and their Greater counterparts), they also only speak of enhancement bonuses, not of magical
enhancement bonuses. Neither do they specify that the weapon counts as magical.
By RAI, I think the "magical" in the description of Damage Resistance is superfluous, and that all kinds of enhancement bonus are intended to make the weapon magical for the purpose of overcoming DR, including the one from Metaphysical Claw.