I tried to understand exactly what kind of access you have, but may have failed somewhere along the lines. I'm probably a little ignorant, so keep that in mind with this post.
Perhaps you could invest in a more convenient, disability-oriented keyboard for convenience?
X-keys have a number of interesting and potentially useful products.
On the subject of keyboards, the program AutoHotkey is excellent for mapping just about any key to just about any action. The program is a little controversial under gaming because it's very versatile and could lead to some questionable actions, hence why I haven't linked it. Either way, I'd imagine it could be very useful to you.
Definitely check out OPie, it was the first addon that came to mind, and Seerah already mentioned it above. It should make things much easier for you on the whole, giving you access to many more actions.
Perhaps this is obvious, but there seem to be a few bindings that you could simply do with the default binding interface. For example, have you tried binding something to autorun?
As for chat, have you tried voice recognition? I'm not sure how this would work with a speech synthesiser, or if there's any PC-based solution regarding that, but you didn't mention anything about speech.
All in all, I hope you find something to make your gameplay experience easier. I think it's wonderful that you're getting so much enjoyment out of the game, and clearly you're putting in a lot of effort into getting around WoW!