If DL is the one operating the flight where you have a seating question, the question should be posed there. AF/KLM and DL have a joint venture, but are différent companies and run different IT systèmes. Maybe the American airlines give free upgrades, but certainly DL does not care about Flying Blue members because even FB Platinums are at the bottom of the list for DL flights.

If you're worried about contrôle passeports at DTW, that's also a question for the DL forum. But I would agree 1h25 is tight considering you must also retrieve bagages and recheck. But DTW is a DL hub and will reaccomodate you if the correspondance is missed.