Filter the "embed Post/Page title" variable

I'm not 100% sure what you are trying to do as far as filtering the post/page title variable? The variable is pre-defined and simply outputs the Post/Page Title. If you want to manipulate the post/page title and use it somewhere you would have to write custom code to do so and populate that value where you want to put it. The form field variables themselves don't have filters.

What kind of data are you looking at adding to the email notifications?

By default it accepts HTML and text you enter in the Notification Message Body and then it also utilized the merge codes for the form data via the Insert form field variable drop down.

Gravity Forms v1.5 supports shortcodes within the email notification message body. So if you try the development release of v1.5 what you could do is create your own custom shortcode that outputs whatever dynamic data you want to display and then have that shortcode output it and use that shortcode in your notification.

v1.5 is a development release available on the Downloads page.