You can create a hyperlink for a new email "mailto:" that will launch a new mail and can have the to and subject etc.
Since the form is in sharepoint you should not have to save it again. You could actually put the path to the specific file in the email body.
The attachment would be trickier but you could either have the user attach manually using the path provided or you could setup an Outlook rule which would automatically detect and use the path to make the file attachment.
For the second I would create another data connection for submit in the form that would save the document to a set location on the local computer. My Documents\rejects or whatever that saved the form with a descriptive name