Indeed, there is no escaping this I had the same problem learning German. :) Sometimes it's so easy: waarom/warum waar/wo wat/was and sometimes it's not: wie/wer hoe/wie. Dutch also have the problem of mixing up wann and wenn in German. Usually wanneer translates to wann, but to add to the confusion, in Dutch there is also a second use of wanneer…witch translates to wenn. And if you include English when in this, and you've found one of the few exceptions where is does more harm than good knowing all 3 these languages…
BTW I think it's ok, but I might have mixed something up here, the reason for that is in this post itself. ;)
You appear to have kept everything straight. But that's another one I'm not quite used to: hoe. I'm just so used to using wie. Eh, you get used to it eventually. I was surprised to see that there was just wanneer, since in German, as you said, there is both wann and wenn.
Another thing I'm surprised about is that even though I've been studying German for a while, since I've been studying Dutch non-stop for the past couple days I find myself trying to say de instead of German articles. Oh, the hardships of being a lanuage enthusiast.