Hi Dybowski,
For 1:
Set up your windows properly and this will do what you what. Make your windows with sizes of say 970 mm width with 15 mm as a shim gap, for your overall rough opening and then you will be able to dimension to the window opening at, in this example, 1000 mm.
For 2: not that I know of unless you enter the wall length as a block module. However then when you join it to another wall, that overall length will change as the wall length is determined, I think, at the centre line. You can use some temporary lines as block module guides and stretch or shrink the walls to be on the module. We do that sometimes.
You should provide a signature that describes your VW's version and computer set-up. This could help in any future questions that you might have.
Cheers.