from my personal experiences the happy ends seem dependent on the 'secondary' stat aside from the trust one (not even taking account the hidden affectation attribute from correct answers) --
daire: design
zane: management
kiron: social (i believe?? i can't recall how i played through his since i did it at like 2-4 in the morning so i'm not super confident with this one, i can't recall how closely i juggled the other stats with his but it seems plausible enough)
while getting every single zane bad end before finally getting his happy end, i decided to just ignore other stats aside from management and trust to see if it'd net me it --- and it has! try doing that if you're having trouble i guess? it worked out for me ... my design and social in that route was pitifully low but i still netted the happy ending (truth revealed). not sure if it has a impact on the other routes if you neglect the non-secondary stat. i pretty much ended up using zane as a guinea pig for how badly i was failing getting a decent ending for him haha
good luck!