Define "open". How many ships is that? Bear in mind that every time you do, you're injecting your opinion as to "how many ships are enough". As an open opponent of this entire effort, then literally any number below 100% for the metric of "Strait is open" you'll define as a failure.

Nonsense. One can point out that a five-year-old is a child while a forty-three-year-old is an adult without having to identify the exact day and date a child turns into an adult. The fact that we can't pinpoint the exact moment of a transition between two states doesn't mean that it's impossible to speak meaningfully about those two states when we're not dealing with the transition point. There is a clear difference between night and day, even though there may not be any non-arbitrary way to determine the precise point at which night turns into day.

If only 2-3% of pre-war traffic is going through the Strait, then the Strait is still closed. Conversely, if 97-98% of pre-war traffic were going through the Strait, the Strait would inarguably be open. We do not have to worry about the edge cases of 43%-57% or 52%-48% to know that the Strait is still closed if 97% of traffic is stuck.

You're trying to dodge, but your statement that it looks like Operation Project Freedom wasn't a failure is clearly wrong. If 97% of the Strait's traffic is still blocked from going through, then the Strait is still closed and Operation Project Freedom failed.