But you're ignoring his mental thoughts, he acts like a jerk and he tries to justify it in his head but slowly you watch his thoughts come to questioning his own beliefs. His gradual change is told internally.

His dialogue after speaking with Ellone in the second disc has him talking to himself about how he should be self sufficient but then he turns around and says he's lying, he's confused and doesn't know what to do, then he he wishes someone could tell him what to do and at that moment, he realizes that he may need people. I believe we get treated with one of the flashbacks of his childhood where he tries to justify to himself why he's walked this path but really if you pay attention to his inner monologues you'll see he actually spends a good deal of time fighting against his own values and slowly realizing (as his comrades point it out to him) that he really is starting to care for others.

This goes back and forth in his brain until Rinoa goes into a coma and he finally confesses to her (well, she was in the coma at the time, how Squall of him ) that maybe he's running away from it all and maybe he's just afraid of getting hurt which is why he pushes people away. From there onward he becomes somewhat more open through the rest of Disc 3

The dance scene is also more important than you let on. Squall doesn't want to do it but as time goes on and he learns not to trip over Rinoa, he begins to enjoy it. Hell, the first time you see Squall laugh (and one of the few times he does) is when he first meets Rinoa. This whole scene is our first glimpse into seeing that Squall isn't a total rule junkie sour puss.

During the reunion from the Missile Mission, Squall actually talks about how glad he is to see Rinoa safe and how he may not have lived with himself had he ordered her to her death. Its kinda touching actually.