In the drink game, the mc has the choice of lie, i think girls lies there with the virgin stuff. Clearly if MC can lie, girls can lie too. Eve said she masturbates 3 time in a week, oh come on, she fucks with Cassie almost this 3 time a week!
In the another point, i feel MC had to fail in this threesome, just because is the less experimented of the three. However, i feel MC had more chemistry with Eve, in solo Cassie love path, he failed, in solo Eve love path, he succeses. Eve said to MC she last long usually (in love/love path, in bad ending route).
In my opinion, all the situation, the throuple thing, must affect more to MC, being the "third wheel" (not really, but almost) all this stuff should impact negativily in his performance.
I believe in his rematch with Eve in this path will be "the redemtion".