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.
This simple scenario presented by the OP shows us how little many people know about probabilities, and there are studies which corroborate this, after all even if the odds of the dice landing on the number in which we placed our bet are still the same, once the payout doubles it is worth to always take the bet as you are now the one playing with an advantage, and yet there are many people that would not take that bet as anything below a 100% win rate seems to be too risky for them.