Unfortunately, there is no way to exactly tell you how much your dream rifle will weigh, given all the variables you list.
However, you may start with the following:
1.- Weigh your rifle in its present configuration, including scope, mounts and rings. This will give you a baseline to work with.
2.- Contact McMillan or the other manufacturers you prefer and ask them about the weight of the type of stock you are contemplating.
3.- Contact Krieger, Lilja or Pac-Nor and inquire about the approximate weight for one of their 26" Light Varmint contour barrels. This will narrow down you final weight.
As far as barrels go, save yourself some bucks (about $100) and go with a Pac-Nor barrel instead of a Krieger. Nothing wrong with Krieger, but nothing wrong with Pac-Nor, either.
While I do not use Krieger barrels, I do use Shilen, Schneider and Pac-Nor and I see no difference in quality between them. As a matter of fact, Pac-Nor is less expensive than either, and will deliver within promised lead time. Best of luck, :cb2: