I think Dalton will thrive in this offense. He is much better than Tannehill. Dalton was not the Bengals problem over the years. In his career he has passed for over 31,000 yards and ,for a surprising stat, he has 22 career rushing touchdowns. In 2016 he was #35 in the Top 100 players as voted on by the players. The Jones' get beat up about some of their roster decisions, but they hit it out of the park with this one.
The stats say the Cowboys got lucky playing against such bad pass defenses so far. But, stats are almost always misleading. For example: Seattle, Cleveland, and Atlanta have very poorly ranked pass defenses. Part of that ranking is that Dak threw for over 450 yards against each of them. This is like a pointless chicken or the egg debate: Did the Cowboys do well against them because their pass defense ranking is bad? Or, is their pass defense ranking bad because the Cowboys did well against them? Of course it can be adjusted for by looking at each of their games, taking out the game vs Cowboys, and re-averaging their pass defense. More number crunching than I want to do, but I think you'll find their pass defenses are not nearly as bad as their rankings would otherwise indicate.
And, I think "fans" who advocate throwing in the towel on the season just because Dak is out are being a bit hasty. This team has glaring weaknesses, but it isn't the QB position.