Welcome to emails in Marketo ;)
I can't see the screenshots you've posted, but the answer is no - unless you edit the HTML and don't use the WYSIWYG editor. As a basic rule, responsive templates should always be edited in code in Marketo, unless you spend the time to really lock them down in a way that Marketo can't add damaging paragraphs and spans to everything.
Bigger clients generally make templates per email (including all copy and imagery), import that, and use it (no edits). I find that smaller clients generally steer clear of responsive design in emails for this very reason.
Marketo are in the process of building new responsive-friendly landing page and email editors, so I'm told - which will be amazing.
It is a default functionality of the editor to wrap the text in the <p> tags. However, the issue that you are facing is not due to the <p> tags.We have tested the same template after the content changes and its looks fine on MS Outlook. (screenshot below).
There might be chances that while editing the content, you might have left any open or closed HTML tag.I would suggest that you create a new email using the same template and edit the content only in HTML code view and not in the visual view.Hope this will help you.
I'd like to introduce you to Knak. Knak is a new way for Marketo Marketers to create beautiful responsive Marketo templates, that just work.
We built Knak for marketers, most of whom do not know how to code. With Knak, you can quickly and easily create a fully responsive email (and landing page - coming soon) with your company colors, logo and social links.
From there you can bring the code into Marketo, where it will just work in Marketo's WYSIWYG editor.
We'd encourage you to give it a shot. Your first template is free: www.knak.io