Dortmund - Duisburg S-Bahn 00:53 arrives at 01:53 which I think should be free with the match ticket (I'm under the impression the free travel ends at 3am) and I've booked a place on a shuttle bus via the airport website ( http://www.airport-weeze.com/en/arriving_by_bus.html - click 'Duisburg') which picks up outside the station at 03:25 (there is a train that arrives at 03:20 but I thought, German efficiency and all that, I'd end up missing the bus) for 17 Euro adult single (12 for a child) and since I didn't pay anything when I reserved I guess you just pay on board.
VRR route planner: http://www.vrr.de/en/index.html