I thought Tribe said he was eligible in his opinion but it is not settled law.
I thought so too, but listening to his remarks on MSNBC a few times, I don't think he offered his opinion, other than saying it took a living constitution approach to find Cruz NBC. He (Tribe) has the same point of view you do, the outcome is unsettled.
I think the outcome is settled against Cruz, if SCOTUS follows the framework it used to argue the Bellei case.