Big guy.
Little bike!
Re: Fenders, check with Gaerlan, they have some Dahon components:
http://www.gaerlan.com/
They might also have tips on extending the handlepost, but I have a feeling that if you go up any higher, the handling would suffer.
You might be able to order through an LBS that's a Dahon dealer, but from what I've heard it takes forever to get in parts.