As much as I like Dak, I think the smart move is to play him against Detroit after the Eagles game. The reason that it would be the smart move is that he needs to be in rhythm with his WRs. The reason that it was a mistake for him to not play in the preseason was because he doesn't have the rhythm with his WRs from having played preseason reps with them, compared to Rush. Hence why Rush is able to move the ball well. Additionally, with the defence that the Rams and Eagles have, Dak could very well injure himself again similar to Romo in 2015 if he comes back too soon.
If he comes back against Detroit, he'll have had two more weeks to recover, and he'd be going against a more favourable matchup at home. Thus, he will have the Lions, Bears, and the Bye week to get in rhythm with the WRs before we play the Packers.