If you have SSL properly configured in IIS, then you should be able to go to either http or https for any page in the DNN app and it shouldn't matter.  No web.config changes are necessary.  So, first I suggest you double-check the IIS settings.

Secondly is the DNN configuation.  There may be a simpler way, in fact I'm almost certain there is I just haven't ever had to take the time to find it.  But what I do is use the SSL Module which is bundled with Portal Store, the full-fledged ecommerce product at www.dnn-modules.com.  It gives me the flexibility to easily pick and choose which pages I want to encrypt, and I can use wildcart certs as well. 

However, if you want to force https for the entire application I'm sure there's an easier way.  If nobody replies with the easier suggestion before I get around to it, I'll try to reply with some suggestions later.  But first, double-check your IIS configuration!