the advice i am about to give you came from a personal male trainer who is in perfect shape.
DOING THAT MUCH CARDIO IS VERY BAD FOR YOU.
Cardio should be 35 minutes to 60minutes that is all your body needs and that is all your body can handle after that your body has no more energy left to use so it starts feeding off your muscle for energy.
Losing muscle will actually make it harder for you to run your marathon and make it hard for you to get in shape. As you will just be thin, flabby and weak rather then lean and full of energy and strength.
When you go to the gym do 10minutes of cardio to get your heart rate going. Then do 30minutes of weights and or machines that will help you build some muscle and help you with strength. After you are done working out with free weights and machines do 35 minutes worth of cardio to 60minutes at the most.
that will not only boost your energy and built strength it will help you get thru those marathons with no problems.
working out for more then 1hour and 30minutes a day will make NO difference in your body the positive way...only negative way so stop killing your self and your body and dont go past 1hour and a half a day.
the only people that need that many hours of work out a day are the people who do body building competitions and are on a lot of steroids.