Marathon Time Prediction

With those training runs, you should be around 3:10-3:20. But on race day, run super easy for the first 20 miles, like so easy that it doesn't feel like a race. Because those final 6 miles are brutal.

It’s hard to say what you could run without you having done any marathon specific workouts.. you might be able to do 18 miles at sub 7 pace but who knows how you body will react after another 8 miles and at a faster pace. With some good indicators in your upcoming workouts maybe low 3 hours. Do some workouts and a simulator workout with 4 weeks left and check back in

If you can be closer to 50mpw consistently over the next 10 weeks & do some 18-22 mile long runs in that 6:45-7:00 pace range then sub-3 is on the table. I think 3:10-3:20 is settling.

As far as workouts go, I would aim for 1.5 workouts every week. Do a weekly threshold session (stuff around half marathon pace or slightly faster straight or broken) with decent volume (maybe start at 6k-8k, build to 10k-12k) (examples: 8 x 1k @ T w./ 1:00 rest, 5-6 x mile @ T w./ 1:00 rest, 3 x 2 miles @ T w./ 1:30-2:00 rest). Then do some work @ 6:40-6:50 in your long run every other week. One weekend it's an easy long run. The next has a tempo in it. Start with 6 miles. Build to 10ish. That should be a good introduction to marathon training/workouts. Looks like you have some potential if you're already doing what you're doing without a ton of structure.

It depends on how aggressive you want to be. Do you want it to be just for fun, or do you want to really push yourself?

If you have already done 18 miles sub 7, and have done a 1:24 HM without straining, I think 2:55-3:00 is a reasonable goal. Maybe even faster if the sub-7 18-miler felt easy.