I also suffer from the desire to know & understand all - which keeps me on this thing far too long - but I will check your link !!

Just for follow up info.

I wondered about the uPNP config as it implies that it is the easiest way to set up the router and avoid all of this manual port forwarding and IP fixing stuff. So..

I deleted all the manual port forwarding I had setup.
Configured for uPNP and did the same in Frostwire.
Restarted everything and it worked flawlessly - even for torrents without a problem.
I also notice that Frostwire starts up much faster like this - maybe just coincidence.

Anyway, thanks for the feedback - I notice you really provide some valued support to this forum it is really appreciated.