How can I see all my reputations points since I joined?
From "Quick Links" in the Forum Bar, click on "My Profile". On your profile page, there's 5 tabs underneath your rep points: "Deals I Like", "Deals I Don't Like", "Voting History", "Reps" and "Reps Given" (your rep history is in the latter 2 tabs).
You can only see your own rep history. Others can't see your rep history, with the exception of mods. And you can't see others' rep history. The latter 2 tabs on a profile page is omitted if it's not your own profile page.