Hitman YES, on that one there is no risk whatsoever. Your worst scenario is a break even, but every game that landed on 3 would win. You only need one to make money.As long as you got those odds and those numbers you could bet that way a thousand times and not lose money.
But that isn't exactly the odd/hold I put up. I used -2.5 +100 and +3 -120. That way your worse odds/vig/hold (-120) has the chance for the tie. Rather than the -2.5 that you have. When you can get a tie it is always easier to eat the bigger number. Not sure of the math, since no one can say for certain. But in real world scenarios a tie isn't a loss, and that tie is a winner the other way for "better" odds.
The only way to work it out is to know every single game outcome in NFL history under these circumstances. Even then it only gives you an historical probability, not a mathematical certainty.
Math is a tricky thing in sports. It is all just guess work, even with all the answers. Because the data is constantly changing. The finish tonight in fact will alter the results used to base a play we made tonight. So while one way might reinforce the play in the future, a finish the other way might tip the scales to the other side. That is why it is very tricky, and actually pretty subjective.
Most guys wouldn't make the play you gave me where you cannot lose. Mostly because they don't get it or won't waste their time for a few nickles. Ironically that is what the books are doing for the most part, and we all know who gets most of the money in the end.