1) It has to be placed somewhere easier to find and more intuitive. VB has it when you click a user's profile link. IPB has it when you view a profile and you see the tabs. Here there is a "recent activity" but it's confusing to me and could indicate blogs, articles or posts. I'd have a separate tab like IPB if this is the route you're going.
2) I don't think there is a view by thread created and posts. IPB does this, vB just lists all posts.
3) Going to the post is a little odd. The link in the Recent Activity takes you to the post but the highlight is for the thread. I'd prefer that when a user sees the link, there is some indication that they are going to the post and not the link for the thread. You might want to (a) have "replied" be a link to the post and "name of thread" go to the thread so the user can read from the beginning; (b) have one link to the post which says made a "reply in thread: abc def ghi" so the entire item is linked. Otherwise it gets too confusing when you look at a thread name to know if it's the thread name or the user's post in the thread and breaks the rules of consistency.