If your app is only used via the web, then there's no problem with embedded
attachments. I use a similar editor and allow web users to upload an attachment
to another document that's normally hidden and then allow them to position a
link to the attachment in the rich text field.
For spell checking, I use something similar to this code:
For this to work, you need a copy of Word on your system and you have to set
the web site as a trusted site in IE, but it's been working well in my apps for
a couple of years in a standardized corporate environment.