So. First kiss. If this is alchemy, there will be three. Jack takes her face in his hands and looks at her with love, and passion, and more sincerity than honestly could have been imagined, given the limits of the character as designed. Which is the point. And Jack says, "Rose. You are worth fighting for." And she is. And he kisses her.
"Wish I'd never met you, Doctor," says Captain Jack, taking the Doctor's face in his hands, very close. Full of love. "I was much better off as a coward," he says, and he kisses the Doctor. That's two. And it is good.
Jack then executes a very Yogi Bear kind of self-launched run toward the elevator, shouting out, "See you in hell!" Already there, that's the point. The Doctor and Rose watch him leave, and Rose starts telling lies again: "He's gonna be alright, isn't he?" The Doctor looks at her, but he doesn't have anything to say: Jack's a hero. He's going to die. Back to ex-Gnostic Saint Augustine and I'll keep it short: as a sincere Platonist and rationalist, his Trinitarian explorations are kind of mind-blowingly Aspergers-ish, as any good saint's detail-oriented overthinking should be. They always start with the friggin' diagrams when it gets too close to the uniterable. But he had this idea about how the Holy Trinity was mirrored in every human soul through memory, knowledge and will. Everything that ever was, the ability to analyze it, and the will to commit to the process -- and that's God, which is about as Gnostic 101 as you can get. And, as he saw it, the restoration of the divine was a three-part act of faith: holding God in your mind, contemplating the truth of God, and delighting in it. Retentio, contemplatio, dilectio. Each of the three supporting the others, leading to a meditative ecstatic experience of God, which cannot be put into words. I think you know where I'm headed with this, but for now: Captain Jack is the Will. Even without his memories, he delights in the truth (and the now) in a way that the Doctor can only get to about half the time -- given his cosmic ADD and soul-crushing guilt.