Hi Paul
I suppose your Norma is a 4X5"
I have a Norma 5X7 with the 4X5 reduction back and No ruler.
I got me a tape measure on which I planned to mark the appropiate compesations factor when needed but so far I just kind of guestimate
@2 One of my lensboards is the extended kind like yours but I never used it since I have the bellows extension I need for the 240mm I use ( it doesn't add much anyway)
If you need more you can add more bellows using an extra front std or acessory std.
Actually there was a 90mm SA mounted on the extended lensboard and offcource it didn't work that way
The 90mm SA is the widest I own and it works fine on the flat boards.
@3 You can shoot for years wanting nothing but the 150mm but a 240-300mm could be nice as could a wide like the 90mm or even a 75mm.
@4 2 DDS is not enough in my experience. I have 6 13X18cm DDS for my Norma and though I havn't used all on a single shooting I'd like to have a couple more. So between 6 and 10 would be my answer.
The Norma is a great camera and solidly build. Con gratulations.
Kind regards