Just a progress report here.  I decided to gove up on using an alternate port. It appears to be a capability that is no longer supported in DNN.  I reinstalled my DNN using port 80, and it does not appear that the ISP blocks it.  I am able to view a basic HTML page with no trouble.  Unfortunately, DNN seems to just hang outside of the firewall.  On the server it runs fine, but outside the router (even with the server firewall off) it hangs on 'waiting for www.domain.etc' with the site name in the title bar on IE, and on Firefox, the site loads, but extremely slow (several minutes), sometimes never fully completing a load. 

I'm not sure how to procede here, but I wanted to provide a progress note.

I did end up doing that, and the portal is running.  I also found out that my issue seems to be more related to the setup of my local LAN.  The DNN portals that I set up run fine on both 80 and the alternate port when accessed from outside of my LAN.  However, when I access them from inside (i.e. another computer in my home network) it loads as slow as can be, and I thought I was not getting it to run at all.  Given enought time, my home computers cached enough graphics that I can bring up the pages, but I still can't manage them.  Of course, that is a different problem :)

Oddly, I didn't run into the 403.1 error that you describe, but one thing to be careful about is that if I used a non-admin account to extract the install files, not all of them were opened.  The .vb files seemed to be screened out.  Other than my odd internal network issue, I'm running fine now.