If you need urgent help, you can post at https://forum.getodk.org/c/marketplace and try to hire someone.
Using the odk-post-receiver in Tomcat doesn't make sense. As it says in the readme, it's an App Engine application, and a Python one at that.
Whatever endpoint you are sending the data to needs to listen for a post and do the needful. https://github.com/opendatakit/opendatakit/wiki/Aggregate-Publishers-Implementation-Details#simple-json-publisher describes what to expect.