I would not take the flight. The trip is for work right? You could also do the right thing and cancel the flight. Perhaps contact someone at your last place of employment (where they bought the ticket) and let them know that you're cancelling the ticket. In a perfect, less crappy world, maybe you could use them as a reference while looking for a new job. They'd have to say you were very honest right?

Also, I would not spend any money on chasing the status. You should focus your time and energy on getting a new job. That's the most important thing, not worrying about a free upgrade or whatever you think status is getting you. Sadly, you never know how long you might be out of work and the bills do keep coming in right?

Best of luck to you in the future.