Agreed with Dajonic. Winter tyres are a must have at this time due to their law. Regarding travelling via Belgium / Netherlands, I've done this trip 5 times already, and best time is a night time.
I always got ferry at 8PM to get me on the continent around 11PM. Then fly through Belgium and Netherlands which can get really busy.
There is a lot of speed cameras in Belgium so be careful there. Also some roads in Belgium are not in a great condition.
Also I would suggest a ferry to Dunkerque it's slightly closer to Belgium than Calais.
Antwerpen ring might be quite confusing, first time I drove with the map only and it was a nightmare.
Regarding trip I would go:
Dunkerque, Gent, Antwerpen, then E34, Venlo, Dortmund and Kassel. There is no toll charges on this route.
Hope you will enjoy your trip :)