I am not able to open your file because I am on an older version of SolidWorks. What have you tried? Have you tried breaking it up into several fillet features? Have you turned off tangent propagation and seen what that does for you?
Have you tried a variable size fillet? Does face fillet get you anywhere? Those are some of the things I would start with.
Luke,.. unfortunately, you have some geometry errors (tools/check or analysis to see,.. which means, you are probably running without Performance/Verification "On" Rebuild ...also, after doing a ctrl-q.. you will need to clean this model up... sorry.