You have two ways to achieve this:
Option 1. Create a custom facet to store newsletter consent for the contact and save its value (true/false) on the click of Subscribe button, the same way you're doing to set email facet value. After values are stored in XDB, you can call this custom facet in experience profile code and store its value in DataTable.
On the custom submit button you will get value of forms fields and you will not get information of pdf template field as this is property of form.
If you want to get pdf template value then create this as a hidden field and then you will get value of pdf template.
Both hidden inputs (fxb_guid_Fields_Index_guid and fxb_guid_Fields_guid__ItemId) usually contain the same value which is the ID of the field item.
If you copy the value and search for it in Sitecore, you will see that it's a field item under /sitecore/Forms/YOUR_FORM/Page/Section/Field Name.
Why it's there? So Sitecore can save it with right id in the ...