1 - It is possible to make an iFrame responsive. Please send them the following link:
http://stackoverflow.com/questions/17838607/making-an-iframe-responsive2 - Browser extensions like Ghostery and Adblock block the browser from loading Marketo forms and the Munchkin tracking script.
One way to address is to display a notification to a user that the form will not load, unless they turn off Adblock. I do not recommend this approach.
A second workaround, which is more work but I would recommend over the first approach, is to detect if the user is running Adblock. If the user is running Adblock, then show the user an alternate form that is generated by your website. Once you have the data from your form, you can do a "server-side post" to send the data into Marketo.
Here is the code to detect if a user is running Adblock:
https://github.com/MurtzaM/Detect-Ad-Blocking-ExtensionHere you can find instructions on setting up a server-side post:
https://community.marketo.com/MarketoDiscussionDetail?id=90650000000PYzlAAGI would recommend working with Marketo professional services to implement this.