Have Form Send Page Data

It makes sense and is possible. Some of the merge tags are already available in the drop down. Add a hidden field to your form, then set the default value (on the advanced tab.) Use the merge tag drop down to select post ID or post title or any of the other available merge tags regarding the post:

{embed_post:ID}
{embed_post:post_title}
{embed_post:post_author}

You can also use {custom_field:[name]} where [name] is the custom field in which you have stored data about the post. If you had a custom field with a meta key of "zipcode" you could get that into your form by using this merge tag as a default value for a hidden field: {custom_field:zipcode].

If you need something else added to your form related to the post, let us know what that is specifically and we will try to help you with a solution.

Please see this topic for an explanation of how to make a field read-only: http://www.gravityhelp.com/forums/topic/non-editable-text-field-request#post-151024

It involves adding a custom CSS class to the field you want to disable (this is on the advanced tab of the field in the form builder) and then a small piece of jQuery added to the head of your page where the form is displayed.