This is difficult to answer, as there is such a broad range of intensity (high Zone 2 to high Zone X) that can be used in this workout, and in marathon racing in general.
Overall, the workout should be “challenging” but not agony. It’s supposed to be the intensity in which you expect to run the marathon. But, sometimes you don’t know what intensity you want to use until after you do the run simulator workout.
So, your feedback would indicate you did it right. “Uncomfortable” is right on for this workout. Remember, you’ve got 6 more miles on race day.
In terms of the 7 seconds…. how much risk are you willing to introduce? It sounds like you nailed the RLMS, so there is some risk in going any faster. Only you can decide hoe much risk, but I can say that you will not be able to maintain low Zone 3 for 2.5 hours, high Zone X is the most you can exp3ect, and that is exceptionally aggressive.
Finally, if your “friends” are the kind of people who judge a person based on how fast they run a marathon…they sound like my kind of people! 😉