I would definitely take that bet, and I doubt anyone with a bare minimum gambling knowledge wouldn't.
Regardiing the best size I would keep it the same size disregarding how much more I will be paid out, because It Is a single bet event.
Exactly. You can expect at least a 1 roll out of 6 to be your number, but with the x12 payout you can technically miss 10 times and still win money. Usually in every game of chance your odds are much lower and it's much harder to make a profit. Like in typical dice you have to score each time with a 50% chance to make money. If you score every second bet you still lose. Here you can score 1 out of 10 with 16,5% chance and make money - it's pretty good.