Okay, so I think I fixed my own problem. It's probably a hackish solution, but if it works, that's all that matters. What I did was remove any of what I assumed to be temp files of main.cf from /etc/postfix/. they look like /etc/postfix/main.cf~n where n is a positive integer. Sometimes this n is absent, but the tilde stays. Then I edited the relayhost parameter as such:
relayhost = [smtp.comcast.net]:587
Here, to my knowledge, smtp.comcast.net is the smtp server that my ISP runs for its subscribers and 587 is the submission port. I also commented out this line
# smtp_sasl_mechanism_filter = login
I'm not sure that commenting it out did anything or what it does when it is left uncommented, but doing this allowed my setup to send mail. So in short, I can now send mail as I could before. I have no clue why it stopped working in the first place though. I'm still waiting on my email from an outside email domain to make sure that I can receive mail again. I'll update this thread once I either get a failure to deliver notice or it shows up in my inbox.