The attack step does not end just because you lose troops. It ends either when you chose to end it, or are forced to do so because of a lack of troops on the whole map.
You will not receive the continent bonus of troops until the start of your next turn (assuming you still control the continent).
The set of 3 cards is revealed at the start of the turn during troop placement, and offers you a one time bonus supply. It will not happen every turn.
Update for change to question: Your turn does not end if you lose troops. You may continue to attack until you either don't want to attack, or have no territories with 2+ troops adjacent to an enemy.