Wow, I admire your ambition but that workout would be crazy. You really do not need to do that much to grow man. Focus on your basic compound moves, eat right, sleep right and you will grow.
There is a definite advantage in weight training your legs when training for a marathon. Particularly on hills. I run and at 200 pounds can not keep up with the "runners build" guys but I can gain on...
I alternate weighted decline crunches and weighted leg lifts. With that and the workout they get as a helper muscle in my other lifts I feel it does the job.
I do them at the end of my chest/tri workout and they make my arms shake. Make sure you keep your arms at a 90 degree to your body and come down as far as possible. You could scoot back on the bench...