Re Hotel St Jean in Sedan - we stayed there and it was very good. Recently updated but, yes, the surrounding streets are a bit run down. The hotel has secure parking in a courtyard behind the roller door for bikes. Yes, the town is quiet on weekdays. The excellent Bar Gambetta closed at 7pm so we went back for a good dinner at the hotel.
Hotel les Pins. Been a while since I stayed there. The restaurant was excellent and
@Gyp and I were able to park our bikes in one of the garages under some of the rooms. Was this not an option for you? A better bet near Haguenau (which is usually clogged with traffic) is to cross the Rhine on the free ferry at Drusenheim and stay in Buhlertal at Hotel Adler
https://maps.app.goo.gl/dfooQ9WeuEMts7eb6
Hotel Florence is a good place to head for on a first or last night in France. Used it a couple of times.