Marathon specific training

do your long run once a week, the main key is just volume, increasing your long run and increasing tempo runs. Start at 10 mile tempos and increase to 12-14. I would do these on Saturdays and keep Tuesdays for a shorter 6 mile tempo or a 6x1 mile workout, not too hard 4:55-5:05 pace for a 15min 5k runner. The focus is to gain as much strength as possible with aerobic power, keep a regimen like this with a Tues/Sat wkt and Sunday long run, be patient, and you will see benefits. Mileage is key.

What are you trying to do with the short intervals? Are you still trying to get speed or you just trying to not lose speed? You could probably dump the short interval workout and just keep speed with strides. I like your long run pace, but it looks like you have a big gap between the distance in your long intervals compared to your long run that you've stopped working. Those were the tempos it looked like you did during your base phase, but you may not want to totally dump those. If anything, maybe do a hilly tempo, steady state, or progressive run in lieu of the short intervals on some weeks.

How are you doing the long runs to get that pace? Do you finish quickly and get that average or do you run really at the same even pace?

You said you've done a tempo run lasting 70-90 minutes and long runs of 16-18 miles. I'm curious, how many miles do these 70-90 minute runs end up being? How different are they from the 16-18 mile runs?

Since you plan to give it two attempts, be sure not to rehash the same general plan twice in a row.

What's your previous experience? What do you consider your strengths and weaknesses?

I liked having shorter intervals during my marathon build-up because I felt it made me more efficient at marathon pace and really helped develop my motor before building marathon specific endurance. It may not work for everyone, but I followed a Renato Canova style approach but modified it somewhat based on my background and time for training, and I ended up running 10:00 faster than my original goal. A rough outline was something like this:

4-6 weeks: Easy running with one progression run a week, no runs over 90 minutes along with 10x10s hill sprints with plenty of rest

4-6 weeks: Progression run and tempo run once a week, with a long run every other week along with the hill sprints.

8-10 weeks: Get in good 10k/half marathon shape. Tuesday was something at around 3k-10k effort, Wednesday was 10 miles at 90% of MP, Friday was just a classic tempo workout and on Sunday, I'd do an easy long run or a long run with a fast finish. I'd run a lot of workouts tired but would still do them. I didn't do the hill sprints because I didn't have time to with work and coaching.

8 weeks: Marathon-specific cycle. Monday was short hill sprints. Tuesday, usually a marathon specific workout with something at HM pace occasionally, Friday was 10 miles at 95% MP, Sunday was a long run, usually with some MP running in it. Whereas the last cycle, I ran workouts tired, in this cycle, I made sure I was recovered enough to run my workouts at MP.