Sub 3 Hour Training Plan

From your training it looks like you are more of a triathlete than a runner. With a full-time job the triathlon focus would make it very difficult to run very well in the marathon. The problem is that in order to get close to realizing your marathon potential you need to run at least an hour every day 6 days a week. Biking and swimming cannot replace it. You can bike and swim in addition, and given adequate rest and proper diet it will not hurt, but the problem is that, I imagine, with a job and a family you cannot afford to exercise 3 hours a day and take a two hour nap on top of it.

The good news is that you have a decent amount of natural speed. If you can do a half in 1:30 already off this type of training, that is a big plus. You just need to double that in the full marathon. What you should do depends on your goals. Would you be willing to sacrifice your triathlon training for a year to crack 3:00 in the marathon? If yes, then start running 7 miles a day at a comfortable pace with the long run of 14. Gradually bring it up to 10 a day with 20 in the long run. Once you are comfortable with this kind of mileage (not just in terms of energy levels, but in terms of injury resistance), start speeding up the final miles of your long run, and if you feel good during the week, throw in something quicker in the 6:00 range during the week as well. Do not race marathons just because you signed up, race them when you are ready. If you signed up, are not yet fit, and do not want to waste the entry, just jog most of it, finish quicker, and call it a long run. Barring disasters you should crack 3:00 within a year.

If you want to keep the triathlon training up, it is going to be difficult, but the idea is to run as much as you can, and do as much of it as possible at around 6:50 pace.