Ya, I was not pleased with how the corners were coming out.

About the posts checking, a possible solution could be to either have the sills come out another 1" or 1/2" and so leaving a gap for expansion, or to just use a smaller piece of foam. I don't want the floor to come up too far past the posts, because I do not want the full width of the posts jutting out into the interior, and I don't want to have to use wider than 2x6's, because the extra costs would defeat the purpose of this whole system. This all makes me wonder, how narrow can one go on the posts anyway?

I suppose if I were to have 2x6's 2' OC for the outside sheathing, and then nail 2x2's on the inside horizontally it would bring my walls in a little more. If I would have the sills out a half inch further, then the walls with 2x2's on the inside would be in an inch further than the previous design. I should see whether 2x6's on 2' c. and 2x2's run horizontal on 16" c. would typically require less total wood than just having 2x6's 16" OC.

About sheathing, I want to use sheathing. Like I said, I despise working on houses that don't have any sheathing, because there is nothing to nail to at times when your really need something. It may save money, but to what extent should I apply this idea of saving money?