I don't know about a WYSIWYG HTML editor, I use nano and write HTML. However, I'm guessing that you could use OOo or AbiWord or some other graphical text editor, and select SaveAs, with the filetype being a html document, although I can't confirm this [I know you can do it with OOo].
As for a replacement for Fireworks, I'd suggest the GIMP. It's more of a Photoshop than Fireworks, but it's okay. I don't think that you can run Fireworks MX under Wine, you'll have to check...