I have seen a previous posted with a reply;
“I’d probably say you’re best option would be to create a new page template. If you duplicate (inside your theme) page.php and name it single-job_listing.php you can then remove the sidebar calls and the other part from the html.
Alternatively you may be able to do it with CSS if the body has a unique class – easier but messier”.
I have tried this and it does remove the widget area, but the job details does not go the full width of the page.
I have the columns set on the job listings page to one column but no joy on the job page full width.