[Optimizer] Full width newsletter subscription form

Hi,
I’ve been struggling all day to create a full width newsletter subscription form in the footer of my website (that will appear on every page). Is there any foother plugin widget out there that can do this, and is compatible with both optimizer and MailChimp?

I have set up a footer widget inside Optimizer’s customizer, but there seem to be 4 widget columns next to each other so my opt-in form is located left. How do I exclude the other 3 and make my only 1 footer widget a 100%?

This is an idea of what I would like to achieve:

Any help would be greatly appreciated! Thanks in advance.

– Feodor