If I were you, the following would be my strategy (tactic is a different issue).
First, you buddy PM definitely is not enthusiastic about your possible promotion. He does not look like your enemy or an obstacle in the way either. Hey, he is just a powerless PM at your level, worrying about his paycheck too. Don't criticize him when you talk to the director. Instead, tell him before you talk to the director: how much you appreciate his support and friendship, blah blah; you understand he does not have the authority and he has tried his best, blah blah; you will talk to the director, will he continue to support you and back you up? Whatever he says is not important.
Second, the director might be the real decision maker. Before the meeting, prepare a printout with all your accomplishments and quilifications and resume. Be ready to explain why you are qualified, what kind of contribution and resposibility you will have for the company. Explicitly mention what support the PM says will give you on this matter.
Third, after the meeting, mention to the PM that you told the director what he told you about his support he promises.
The bottom line: focus on the business; show positive; even if you will leave out of fear of retaliation, you will still do you best going after the promotion --- which will be a higher step stone for next level.
