Letter of recommendation deadline

My professor has agreed (in person and through email) to write me a letter of recommendation. I requested it in mid September and he told me to keep bothering him about the letter until he does it. Throughout the last two weeks, I have been resending the request on PharmCAS as well as emailing him. He replied 10 days ago and said it will be done that weekend. This weekend rolls up and still nothing. I know it is my job as a student to make sure that the letter gets done, but the professor doesn't even reply to many of my emails.

I was thinking of emailing the professor tomorrow to see if he needs help. At this point, I was also wondering what my other potential options are. He's the only professor I asked since he agreed to do it.

TL;DR Is it crucial to have my letter of recommendation sent in before I submit my application? Will they rescind my applications to schools due Nov 1? Does anyone else have the same problem? What else can I do on my part to expedite that letter?

Thanks in advance everyone!