i'm operating as a casino and offering prop bets to players. just wanna make sure my odds and rules are +ev

Rules

u can see your hole cards before betting
max betting differential of 1k (eg 3k on big and 2k on small)
max bet of 200 on river if player didn't bet on flop or turn
A to K = 1 to 13 points respectively

Payouts

21 points on flop, banker wins all bets
betting on < 21 points on flop (small) - 1 pay 1
betting on > 21 points on flop (big) - 1 pay 1
betting on 21 points on flop - 1 pay 13

betting on turn or river 7 - 1 pay 40
betting on < 7 points on turn or river - 1 pay 13
betting on > 7 points on turn or river - 1 pay 13
banker wins all bets on turn or river 7

1) how do i calculate the probability and ev of 21 points happening on the flop given the odds i offer?
2) are any of my payouts -ev?