Optin form – square box and placement on index pages

Hi

thanks for creating such an easy to use optin. I have two questions that I hope you can help with

site is https://fromthepoolside.com

1) is it possible to have the box square and remove the round corners

2) the optin box appears on the index pages and also make some coding (from my theme) appear. If you go to that page
https://fromthepoolside.com/category/holiday-rentals/page/2/
you’ll see what I mean
How can I prevent that from happening? I don’t want the box to be on those index pages.

Thanks