Thanks for the chapter!
I can get the MC's anger and disappointment, but he really should take off the rose colored glasses. Did it ever occur to him that the reason the princess knows the contents of his room and chases off other girls is because she really likes him? Granted his grades and abilities can't compare to his father, but being second to only Fiancei is really good, heck I'd love to have been able to keep coming out second in my grade back when I was in school struggling to get everything down. Also, shouldn't try to shoulder unrealistic expectations of other people who only gossip and comment on their ignorance.
As for his father's bragging I'd say it was more pointing out vast difference in immediate hands on experience by going directly into life or death battles versus a more peaceful and less dangerous school environment. Also, I think father really is busy with work and part of reason doesn't teach is most of what he does is instinctive and hard to teach along with being the dangerous sink or swim type lessons. You know like how Roxanne in "Isekai Meikyuu de Harem wo" describes her ability to fight and/or dodge as simply going oomph when the enemy goes bamph and other things which only make sense to her and nobody else.
I wonder if that maid is really demon kin. Although she has a lot of insight and pointing out things MC is glossing over such as the father was really struggling in school. Seems even slept through various classes.