Head-to-head tiebreaker is over, no longer relevant. Next up is the division tiebreaker, assume they end up tied there too. Next tiebreaker is common opponents. This is where a Philly loss in Seattle is huge. It would give Dallas the division if they both end up at 13-4 and Dallas can only lose to Detroit(won’t happen).
If Dallas wins out, they only need Philly to lose one more game, doesn’t matter to who. The Cowboys next two games are common opponents(Buff and Miami) and Philly beat them both. So, if Dallas beats them both and Seattle beats Philly, Dallas holds that tiebreaker.