Tens and face cards count 0. Other cards count their face. Only the last digit of the total matters, so 15 is 5. A third card is drawn by fixed rules, not by choice. You do not hit.
Banker wins more often, and the table usually takes 5% commission on a banker win. That leaves a house edge near 1.06%. A tie bet pays more because ties are rarer, and the edge on the tie is much wider. This site has no baccarat demo in the slot library.