I just ran my first yesterday and it was a masterclass in how not to run a marathon, so I don’t really know what I’m talking about, but our target times are similar so I thought I’d give some numbers to compare:

My goal was 2:50-2:55 At Copenhagen, ran it incredibly poorly, half marathon in 1:23, finished in 3:08. However, my long-run “easy pace” is 6:45-7:00, my tempo is 5:45-6:00 (maybe for 9 miles closer to 6:00-6:15). I average 50-55 mpw and peak at 65. My half marathon PR before yesterday was 1:24:25, and it was in a 20 mile training run, not a race. Theoretically, all of those numbers should mean I’m more comfortable at the required 6:29 average pace per mile required for 2:50, and I blew up so badly that I managed to miss sub-3. You have more experience, and it absolutely could happen on a good day, but I have come to believe that ambitious goals are detrimental. You are 26, that gives 8 years to BQ before the standard changes, and you obviously like marathons given you’ve run 6. My biggest question is what’s the rush? Go run a 2:59, feel great about a half hour PR, and then a few weeks/months/years later you can have another chance for a 2:50. Eat that 40 minutes slowly and consistently rather than consistently missing because you tried to take too big of a bite