Third-Party Integration with HTTPTargetConnector. Unable to send correct Request Message.

To preface this, I'm relatively new to PeopleSoft/PeopleTools and have been learning everything (Nodes, Messages, Connectors, Listeners, Application Designer, PeopleCode, etc.) as I go for the last few weeks and have hit a roadblock that's been halting me for a few days now.

I'm trying to set up an integration between our PeopleSoft Installation (8.53) and the third-party application but since I'm new (among other things), I've been trying to setup the PeopleSoft Installation to use this calculator web service I read about in a guide. Right now, I'm more focused on just getting a successful request to the service and getting back a response, just to prove that it can be done the way we'd be doing it with the actual application. I've been steadily making progress by trying things out and reading a lot on the Integration Broker until I got to the point where my PeopleCode is creating the XML for the Request Message being sent to the third-party application. The way it's being triggered is by clicking on a simple button on a page I