After many attempts at figuring out the problem, I finally was able to somewhat fix the issue. I had to restart my computer over 5 times. I emptied the iMovie cache. Finally, and the thing that worked the best, was I found a corrupted clip in the video (it was grayed out), and after many attempts, I was able to delete it from my project. I also deleted any grayed out videos from other projects. Then the sound started to work for this project. I was also able to view my project in full screen. I restarted my computer once again, and my project was there, and viewable! However, my project wasn't the most recent version, random things were deleted...but it's better than having to start from scratch.