First of all, you have to make a difference between the HTTP Trigger and an HTTP Request.
The trigger, like I said, is used to "listen", which means its main purpose is to "receive" an event. The request is an action you can set up when receiving a message.
The tutorial you read from Usahidi only uses HTTP requests.
It looks like you've correctly set up your request action, though. The "hits" incrementing is a good sign. If you don't see anything on the Usahidi dashboard, this means that you mistyped the address you in the "external command" dialog for some reason, or that the Usahidi server is down. Every single character is important, so I typed it for you, just in case. Paste this in the address field of the external command:
You'll just have to replace the ***** signs by your own key. (By the way, if you can reach someone at Usahidi, I'd suggest they give this address as a text that people could copy and paste, instead of copying it by themselves. I think it will avoid this kind of problems ;)
As for HTTP trigger, if you really want to use it (which I doubt for the moment), the port is "totally" up to you. There is some kind of protected ports, but you can do pretty much what you want (I often suggest the 8080). This port is absolutely not related to the "port" on which your device is connected on your machine.