"Who are you calling wicked?" The Lady that watches smiling, while her son was beat up in front of her. Fair enough? Cause she would have deserved to be called worse things.
"You got to train more." Strong words coming from somebody with talent (or at least a strong interest in this stuff). Bitch should take her own advice and learn more. Just imagine she would be violently punished for each pop-quiz is fails.
Also maybe it is because of his unyielding will to survive, that he doesn't want to become a knight or adventurer?
I know they are family and for some reason he still loves them, but I don't understand how a grown up (on the inside) character can tolerate that much bullshit. Being beaten up be his father (some chapters ago), then being beaten up by his older sister after being exhausted and then being beaten up by the family friend. And also don't forget: No use of magic! Because if he evens the field, he wouldn't learn as much. This is how you make the most out of his sword fighting skills, no doubt. But this is also how you make a human demon lord. Though he'd never be as strong as his sister with the sword, he still has magic and therefore no shortcoming any more. Go and plunge the world into darkness. If it wouldn't for him being reincarnated and grown, he'd learn that only violence matters.