Good day Content Assassin,
As discussed, I took some time and had a look at the Aweber, GetResponse, MailChimp, InfusionSoft APIs and the Facebook Leads one, I understand the need of the business and I can cover on this project its core only, no UI/UX as that is definitely another project, By its core, I mean, setting up webhooks for Facebook and automatically posting to each of the aforementioned APIs, you might also persist those emails in your own database for more marketing purposes. I will create a php based backed to accomplish this, code will be written in a professional way so you can easily extend the project in the future so it suits your needs accordingly.
Regards
Raú Celis