Require using the absolute path, not relative, to avoid potential conflicts with misconfigured include_paths on assorted hosts.

WordPress coding patterns near-exclusively tend to prefer absolute
paths over relative paths.
Only set up the WordPress admin page if we're in the Admin.  Otherwise it's just needless CPU cycles for every page load on the front-end.
Normalize space-based indentation to tabs, change inline alignment from tabs to spaces around old-line 613, new-line 587, normalize spaces between functions, purge trailing whitespace and indentation on blank lines. Correct docblock indentation to align the left-hand stars.