Good luck with Goofy
Normal weight loss nutrition guidelines don't really work as well when you're in the last stages of marathon training, especially when you throw tapering and race week in there. Setting your tracker to reflect your actual calorie burn is a good start, but it may take a lot of experimentation to figure out what works for you nutritionally during that time period. Unfortunately, there's a reason not many people lose while marathon training.
If you haven't joined already, there are some good marathon-related SparkTeams on the site, and some of the members there may be able to offer some good insight as well.