Looking at the way he's thought about Ageha the whole manga it fits. He looks up to and respects her gaming skills and so he felt he needed to equal (or at least approach equaling) them to be worthy of being her boyfriend.People find his confession to be stupid, but you have to remember......he's a kid. This is his first relationship. The premise is set around games. I did find it a bit of a round about but I see it as him finishing these challenges as a way to feel worthy. He set out finishing impossible games, finally feeling worthy in his eyes to ascertain of a life long relationship.
My guess is that dad does not really care about confession part, but he is all for gaming partnerAight, all bets on the dad being a gaming addict?