Thanks for posting your concern regarding your setup with the MiFi 4082. The Sprint network blocks port 80 for security reasons. Try replacing port 80 with port 8080. Hopefully this helps. Let me know.
I have a MiFi 4082 along with a static ip tethered to a cradlepoint router. if I get on the wifi to the router I can use the ex or the internal static ip to access my web server, but if try to access it from the internet from a different network it will not work. I have the server setup on port 80 and have port forwarding setup on the MiFi and the router. my web server is sending status emails over the internet and i recieve them fine. If you can help send me an email at firstname.lastname@example.org thanks