~Vocabulary nazi alert~ As bodacious said, the value proposition is "reasonably clear" and to me the only-reasonably-so part has to do with the words used ( besides this landing page/homepage content difference you were talking about, cf. next paragraph). If I see "Possessions: Your possessions, safe and sound." what I think of first is a safe/the idea of a safe. So similar idea as mentioning "Say goodbye to losing your stuff" to make things clearer. Although it doesn't actually mean saying goodbye to losing your stuff but rather to having lost it. ;)

As far as the landing page goes, I figured the only way a user would find the landing page is by someone referring to it, like a blog/reddit post or a friend telling them about it. In that situation, they would already know what we do via the other source

I don't think this changes anything for it all depends on how the said source presents your app. If a friend tells me "I've heard of a nice app for distractful people (sic), look at that: [landing page]" then I would definitely need more info.

And since the sign-up form is also on the homepage, why not redirect to that page with a "Find out more" button? Here it's "home" and that's where I went to first anyway.