I understood a full time degree to require 35-40 personal study hours a week, outside of contact time? This is what my lecturers told me. I don't think you have factored that in to your sums.
Depends on the degree. Some degree subjects don't really require a lot of research etc. My son did a Maths degree and basically ignored the "reading list" they gave him. (As did everyone he knows on the course, and the same was said by students in Uni open day subject talks at different Unis!).
He just worked through the materials provided, i.e. printed off the lecture notes, lecture slides, sample questions, past papers, etc all from the Uni portal, and just worked through them, learned them, etc., as he went along. His best guess at the time he spent outside formal "contact" hours was maybe 2-4 hours per week per module, and he'd do 2 or 3 modules at a time, so anywhere between 4 and 12 hours per week, which he'd do in the evenings or spare time in the Uni library between lectures. I don't think he ever did any studying at the weekends until exam season.
The thing is that he was very disciplined, so didn't waste time fooling himself he was studying when in fact he was on social media or half watching TV or you tube - he'd turn off devices and "lock himself" either in his bedroom or a study pod at Uni, and do the work. So an "evening" spent studying was genuinely a full 2-3 hours of work, and not 30 minutes of work between a couple of hours of distractions!!
Obviously he spent a lot more time in exam season going over it all again, but even then it was probably 5 hours per day on average, so he may have hit the 35-40 hours in the 6-8 weeks between Easter and end of Exams, but then there was no contact time as formal "teaching" stopped at the Easter break.
He just got a First, so not bothering with research and the reading lists didn't do him any harm!