You are not on the ground so why would there be moisture coming up through the concrete, and the same question regarding using treated lumber. Both are only required when installing over concrete on "grade". As far as securing the 2x6's construction adhesive will keep them in place until the floor is installed, and once that is done the weight will keep them in place. What is under the concrete will determine with it needs insulation or not. Number 4, installing the subfloor, is correct, however.