What does David’s explanation to Saul of his combat experience say about David’s faith? David is not boasting in his abilities, he is boasting about God's abilities.
How lethal is David as a warrior? With God as his primary weapon, he is absolutely deadly!
Why do you think Saul allows him to go out to battle Goliath? Saul has no other options and as stated in the lesson, he knows that if David loses, the phycological advantage gained by the Philitines would be lessened by Goliath beating a boy without armor and weapons.
Does Saul have faith? If so, what is the source of it? Saul does not have faith, he is hedging his bets.