Can you combine Dark Devotion and Distressing?

Not in the way I imagine you are thinking. Distressing affects YOUR terror radius and Dark Devotion moves your terror radius to the survivor set at 32m. In fact, if you run Dark Devotion and no other perks on Wesker, even with his 40m terror radius, Dark Devotion will still set the terror radius on the survivor to 32m.

Correct. It's basically a "fake" terror radius on the survivor combined with undetectable on you.