I think you should use the tfoot tag, since it's semnatically designated for this type of stuff. But, like many things in HTML, you aren't forced to do it one way or another - you've got some liberty.
This particular example would suffice either way - as a simple TR containing a TD (with a colspan if necessary), or a TFOOT with a TD (with a collspan if necessary).
As far as adding links within the body to jump to the footer, it's awfully nice from a usability standpoint. But that type of thing isn't objectively answerable - it depends on what your project requiremens are.
You can't put a TFOOT just anywhere within a table, ther are rules (<td><tfoot>...</tfoot></td> would be a no-no). For proper use of the TFOOT tag, consult http://www.w3schools.com/tags/tag_tfoot.asp