Okay, here's my take on each of the 3 scenarios.
So clearly this is the preferred outcome, but in my opinion the low probability of conversion and consequence of not converting is too great, when looking at the other scenarios.
I re-ordered your outcomes for clarity, so the 0 first downs and 1 first down outcomes are grouped together.
If the Chiefs have not secured the first 1st down, depending on the time remaining in the game and remaining yardage, they could attempt a FG if they believed they couldn't convert on 4th down. Kicking a FG could be smart there depending on the exact circumstances and how confident they were in their kicker, (who had missed a couple already).
If the Chiefs did secure an additional 1st down, they would be at the CLE 22 (at least) and look at ending the game. From that field position I believe they would go for it no matter what, completely taking the FG off the table. Because with a little over a minute remaining, the reward of 4th down conversion far outweighs the risk of failing, because with that clock and field position, the higher difficulty task for the Browns offense would be scoring a touchdown at all, not getting the 2PT conversion.
I agree with you here that if the Chiefs don't convert a 1st down, they would punt. So we can take the go for it scenario off the table there.
If they do convert a 1st down, they would most likely be fine either way by punting or going for it, and the time and yards remaining would be the biggest factors here in what they decide.
So having gone through these, we can basically map each outcome 1:1 for each scenario and evaluate that way in the decision to punt or not punt. I'll put the non-punting outcome on the left side and punting outcome on the right. Because of the variance in punting distance and kick returns, any scenario that's within 5 yards of the one being compared we'll call even. Any outcome that's significantly better when compared head-to-head i'll color green.
Chiefs not securing a 1st down and making a FG VS. Chiefs not securing a 1st down and punting
Browns would have to score 8 points at their own 25 vs. having to score 7 points at their own 20 with approximately 3:00 remaining.
This one is mostly even, but having to convert the 2pt conversion here should give a slight edge to the punting scenario.
Chiefs not securing a 1st down and failing to convert on 4th down VS. Chiefs not securing a 1st down and punting
Browns would have to score 7 points at their own 25 vs. having to score 7 points at their own 20 with approximately 3:00 remaining.
Mostly even, slight edge non-punting.
Chiefs not securing a 1st down and missing the FG VS. Chiefs not securing a 1st down and punting
Browns would have to score 7 points at their own 35 vs. having to score 7 points at their own 20 with approximately 3:00 remaining.
This one the advantage goes to non-punting. However I strongly believe that Reid would only kick the FG if he believed the probability of making the kick was much higher than the probability of converting a 4th down, making that outcome fall on the less likely scale.
Chiefs convert a 1st down and fail to convert on their second 4th down VS. Chiefs convert a 1st down and punt on their second set of downs
Browns would have to score 7 points at their own 15 vs. having to score 7 points at their own 10 with approximately 1:15 remaining
Mostly even, slight edge non-punting.
Chiefs convert a 1st down and fail to convert on their second 4th down VS. Chiefs convert a 1st down and fail to convert on their second 4th down
Browns would have to score 7 points at their own 15 vs. having to score 7 points at KC 45 with approximately 1:15 remaining
This one the advantage goes to the punting scenario.
Chiefs convert two 1st downs VS. Chiefs convert two 1st downs
Browns lose
So of all the realistic outcomes, we can see that 4 end up even, 1 outcome advantage non-punting, and 1 outcome advantage in punting. But for the full totality of evaluation, we should also include outcomes that are only available in one particular scenario:
Browns convert 4th and 9 VS. N/A
Drive continues vs. Drive ends
Chiefs score touchdown VS. N/A
Browns lose vs. N/A
So here we have one more advantage that favors non-punting, and one more that advantage that favors punting. But as we previously discussed, the odds of 4th and 9 conversion are low, and the Chiefs scoring a TD possibility should be taken seriously...because that is an outcome that can happen with non-punting regardless of 0 or 1 prior first down conversions, so it's always a threat.
I think that additional outcome of an instant loss is reason enough to punt, but even if you think that it's close enough to be even, and if the outcomes are even you should err on the side of going for it, the decision then should be based on how much you believe in your defense.
If you believe your defense won't surrender any first downs, you should go for it.
If you believe your defense will surrender one first down but not two, you should punt.
If you believe your defense will surrender two first downs, you're going to lose either way.
Punting is the better move if you are not confident in having a stalwart defense, because you have more wiggle-room. Going for it is better the more confident you are in your defense, and especially if the other team's kicker isn't good.
The other reason to go for it is if you believe your defense is so bad that it can't stop the other team from getting two first downs or a touchdown. This option is basically a hail mary because you're banking your entire season on the success of the 4th and 9 play. I don't believe we were in a hail mary situation with 4:19 left in the game, so I was fine with punting.
