Agree I definitely don't care about their age gap since they don't really look that much apart. Ji Hoon looks manly and handsome for his age which is more suitable for this type of drama where it involves a lot of dirty tactics. Younger-looking actors/actresses would sully the whole look of the drama.
I doubt her father will redeem himself. He'll probably be used more so for Mr. Song's benefit. I hope that lawyer Ga Gi Hyuk at least redeems himself instead >< In a way, I'm impressed how they developed his character to make it a bit more realistic.
Sometimes, there are no perfect friends who would choose friendship over something else that matters to them more (ex: their love life, family, career, money, etc.) But I hope the drama wraps it up nicely to repair his relationships and become that cool, nice guy again. Don't want him to stay as a betrayer til the very end. I enjoyed his character a lot in the beginning ><