I make my forms in Dreamweaver, too, and if you have a textarea in your form you definitely can't use a WYSIWYG text editor because the editor itself is a textarea.
What I do, to include the form in a content item, is install the kl_php mambot (which lets you use php code within a content item). Then I upload the form file to the server and in the content item type this:
{kl_php}include("myform.html");{/kl_php}
This will insert the contents of myform.html into the content item wherever this code is placed.