I wish I had seen this thread earlier. I’m encountering similar difficulties, which I posted about in a separate thread : How to publish a Monogame project
The easiest way I’ve found to share files is to sign up for an account at dropbox.com. You can upload files there, and share the link with others.
I’m not sure if it helps, but I uploaded my project: https://www.dropbox.com/s/umqv8f7qqtnyky5/monogame_test.zip?dl=0
I’m not sure if we’re experiencing the same problem or not, but they look similar. I think my project is just missing the content files, but I’m not sure how to configure Visual Studio to include them.