First part is factually incorrect. boa df works because of impure feelings.
Bb over relying on fruits will be his undoing but against Luffy. Law isn't that man.
Also, BB has strong haki because he is PK level antagonist (assuming he won't doesn't make sense) and he was the first one who commented on Luffy haki is growing in ID when we didn't even know what haki truly is.
How BB was able to gauge Luffy haki is growing without he himself having good haki in the first place?
Law is just weak hype tool and his fight will lead to another big plot. Him pushing BB to extreme goes against common shonen logic and him escapism just makes the purpose of the fight mute.