1) The charge curve will probably be the same as the 54kWh iD3.
2) Just because you’ve been driving doesn’t mean the battery is warm, moderate speeds on flat motorways, don’t heat the battery. Try setting the charger as the location in the onboard nav, the car might preheat the battery. Try driving faster as you get near the charger.
3) Smaller batteries charge slower than bigger ones. You just have fewer cells to share the electrons between.