he eats at the moment 2 full size mice or one medium rat every 3-4 days, but thats only because he was neglected by his previous owner and when obtained by me a couple of weeks ago VERY hungry and actually lept out of his viv to take the food.
Normal feeding should be about 2 mice per week dependent on size, yours should be about the same size as mine, i am no expert on these as i have just recently got my king but i suppose they will only eat what they want and re-freezing mice seems ok as long as it is only done once or twice as the freezing and defrosting process breaks down the mouse. (assuming you will be feeding frozen)
from material i have read kings seem to be virile feeders when first feeding mine i gave him one medium rat and then offered fuzzies which he gladly took three of then showed no interest in the fourth leading me to believe they only eat what they need.
hope you have as much joy from your king as i have had with mine,.
i owned a blackneck garter, bull snake and a ball python but by far the most enjoyable snake has to be the aptly named KING