Setup custom API action in Formidable plugin

I have a website build on Wordpress and Formidable Pro plugin. I have the Formidable API add-on installed. I need to send data from a form to a partner application with json. It´s application that is being sent from my site to the partner site. The partner has provided full documentation. I have the following challenge with this: 1. I need to have a custom header, because the api key need to be sent in the header. Formidable don´t support customizations of the header in the api action, and the autorization is failing in partner application. 2. I have some conditional fields in my form. Formidable will send blank values in the json, and this is a problem, because the partner application will not accept blank values. So I need help to setup a api action according to specific criterias. 3. I now have a view with an overview with all applications. I need to be able to setup a system so I receive the callback from each application. Partner is returning response code and message in json from each received application. 4. The social security number and account number should be validated through the api directly after the user has typed his or her social security number and account number in the fields in the application form. All custom coding need to be done in front-end, in the plugin "Code snippets". The reason to this is that we have a complex working website, and we can not have any backend coding on this site.