How does the dream show that Tracy is trustworthy? At best, she becomes sympathetic because we see that she's in conflict with herself but the fact is that in the dream Dark Tracy is dominant. The reckless, wanton, devious side of her personality is in control while the other is upset because she's hiding something. And that's all that we know from the dream. There's literally nothing there that would suggest to me that I should trust her with the truth. In fact the only dream to do that would be the Mother's.
Except the threesome doesn't happen unless he's honest to Mom about his interactions with Alice. If he lies, they end up going down the anal route, which never happens in the nightmares. Furthermore, in the nightmares there's a scene between Tracy and Alice where the MC winds up
. And a further nightmare where Nora shows up and appears to speak directly to the MC.
Rather than representing his desires, the nightmares seem to be situations where the MC is no longer in control or able to influence events. Whether this is because he hasn't mastered the night walking ability or because an external force is trying to suppress him through the dream world is hard to say.