1) The only cards that are put in a row on a battlefield are the ones with a poker chip on them or cards that block rows. All other cards played from the deck are one shot cards and are discarded immediately after they are played. Correct?
2) Once a card is played on the battlefield, it remains there for the duration of the game unless it is removed during an attack or by the play of some other card. Correct?
The player of the card can also voluntarily discard his card(s) from the current battlefield.
You can game the game with Ned McReady: Play him (to use his enters play, kill 1 bandit effect", discard him, use the "discard pile to hand" card, play him again (for another kill), discard and use "Shucks... Flesh Wound" to bring him back straight to play from discard (another kill). Assuming his 5 Firepower is enough addition to beat the Colty total, you bagged four kills this turn. For Colty the options are less powerful, but with the 1 Firepower card that forces Colonel to discard a card when it is played + 1-2 Saddlebags, you might be able to get Colonel's hand empty, ideally getting rid of those cards I mentioned in the Ned McReady example above and/or the Manolito card that kills 2 bandits unless you discard 2 cards.