So predictable

You didn't figure out the whole subplot from the first scene because there are no hints to it in the first scene. What you figured out was that Ivan was a figment of his imagination and that most of what was going on was in his own mind because he felt guilty. And you figured all that out a few scenes in, once the hints started dropping.

And that's fine, because it's pretty clear they wanted you to realize he was crazy from pretty early on. It's not a problem with the story.

Wveth!

I think the subplot is obvious right away to just about everyone. The movie is advertised more or less as a man losing his mind, so Ivan shows up as a 'new guy at the shop' and he's introduced when only Reznik is around, and while he's drifting into sleep.

Later they meet at the bar, the bartender doesn't acknowledge him and looks at Reznik like he's crazy. It's spoonfed to you at this point. I think the reveal at the shop is for Reznik, not you the viewer.

Early on it's established, he's crazy, he's hallucinating: From there it's more about being along for the ride as the blanks are filled in. It's been said you can see the ending coming from after the Route 666 carnival ride. I don't believe you'd know the 'whole subplot' from the first scene.

I knew something happened with the kid, I just didn't know exactly what. I cried after the big reveal simply because that's a deep seated fear of mine. Negligence or no, had that happened to me I could have gone on living.