Congratulations on your marathon time! I am sorry about the Tokyo marathon.
To prepare for Boston, I recommend that you take off running completely this week. Then, pick up the plan again for the final 6 weeks until Boston.
If I understand correctly, you really began to fade at kilometer 36. Based on your HR and feedback about your legs, I think you would benefit from a strength training plan for the next 7 weeks. That will likely give you the additional muscular endurance necessary to get through that last 6K.