There's no deviation required here... you need to hang out at the house, and you need to dance with Eva, and you need to help out at the house whenever you can (including cleaning after parties, helping with a house tour over parents' weekend, and attending frat meetings)
The "only" weirdness is that Adam isn't always a fan of you including Tom in activities, and Tom doesn't like it when you encroach on his time with Eva. So there are a few opportunities to hang out with more than one of them that you actually have to turn down (for example, don't have dinner with Eva and Tom after the dance event)
The secret route here also actually triggers after the usual ending montage (I believe YAGS' Adam route was before the montage?), since it replaces the usual "Elliot had a crush on you blah blah" part at the end, which maybe makes it even harder to realize you've gotten it
Apologies again... I didn't intend this to be so fiendishly difficult. A new build will be coming (probably next week?) with a Super Easy mode (unlocked once you complete the other four routes) specifically to address Elliot's route