Hey Benjamin! We are aware of the Mailchimp issue and are working on a fix. I'll message you once it's pushed to prod. :)
Hey Benjamin! You can now embed Mailchimp opt-in form. Just go to your dashboard -> Widgets tab and enter the Mailchimp embed code. It'll appear on your blog home page and at the end of every post. Be sure to choose the "Horizontal Form" from Mailchimp so that it looks good.
Also, I would like to get quick feedback on something -- Would you like to display the form only on your post pages or both homepage and post pages?