This game was created a LONG time ago. The game is called Red Dog, you can find it in a lot of online casinos. Depending on how many cards are in between the first two cards determine the payout. There are different payouts and the game has less than a 5% edge.
Sorry to burst your bubble.
That game was really different from this one. This game always payout 2x of your bet in any way as long as the card is in the middle of the first 2 cards. And if the first 2 cards are same cards, the player will have to choose hi or lo and will get 2x of his money if he guessed it right.
Problem with your game is it has too high of a house edge and this no one would play it. Red dog offers higher payouts for when for example a 6 and 8 come up and only a 7 would win your bet.