Sidebar dropping to the bottom on "older posts"

Start by sorting out some of the 72 markup errors.
https://codex.www.ads-software.com/Validating_a_Website

the major error is an unclosed div in the post ‘Join My Team’ –

(you can see the same sidebar error if you click on that post.)

edit the post in the html setting of the editor, and make sure that all opened divs <div> are closed with a </div>

That was it! Thanks a ton!