I'd call them observations not assumptions. "Sean and Amelie had hardly moved in their cots, let alone woken up, despite the commotion in the apartment."
"Madeleine was snatched apparently without making a sound" Well who heard her?
I think assumption is the correct use in the case of Kate saying "Madeleine was snatched apparently without making a sound"
How could Kate possibly know her daughter was snatched from her bed, and how could she know her daughter did not make a sound as this snatching took place-if she wasn't there?
The suspicion is: the children were light sleepers, they had woke during the night we know this because of Mrs Fenns statement and Maddie also asks about being left alone and waking up, and we are told they left and used a certain entrance so as not to wake the children.
However, on this occasion this one night we have shutters Being jemmied, cold night and the window is open-blowing curtains, banging doors, more checks than usual for that week by various tapas crew, lots of people in and out the apartment- the bedroom. parents screeching- people shouting for MBM in the vacinity. and the children who could wake up with a light on or door opening slept through all that. Yes. that does rouse suspicion.