Nope. People need to understand this: Blocking is not "incomplete." It is simply NOT the case that "people are blocked but not like TOTALLY blocked they're only KINDA blocked" -- bullshit, no, no, NO NO NO. People who are blocked *are* "totes reallyreally blocked". Blocking works exactly like we want it to. It is not incomplete.
Primarily, you must understand that this is a forum. Your profile page/wall/whatever you want to call it is a page on a forum. A forum is a... well, look it up, the history of the very idea of a "forum" implies that it's public and anyone can come and speak their mind. In ancient history, it was much more restricted to the aristocracy, of course. We give you, though, the ability to decide whether your profile page is public or "invite-only." That's as far as it'll go.
No. Not ever. It's a forum. You don't become King of Shit Hill just because it's "your post." If you want private messages, send them. If you make a post, it's public, and you need to recognize that, even if just for your own safety and security.
"an app for this site" -- we have that. It's called "this site." It's a website. It's accessed using standards and protocols established by the World Wide Web Consortium since 1993 so that it can operate on any web-capable device running a standards-compliant web browser. Pretty ingenious, really -- the web exists, so we used it.