Where is the 3" of foam going in the attic? If across the underside of the roof deck to create a sealed attic, you are going to need more than that to be up to code and proper.

Also, spraying directly to the roof deck is not advisable. If you ever need to replace the roof and a piece of plywood, you will loose the foam at the same time. That makes that piece of plywood very expensive.

If you are putting 3" on the attic floor, that is a huge waste of money from the stand point of air sealing.

How are you getting 2" of spray foam on the walls? Are you ripping down all the drywall?

Your project is intriguing to me and I would love to help give you any advice that I can.

As far as window advice you would need to give us an idea of what type of windows your looking to use and what your looking for these to do for you?