Raising a sunken living room floor and concerned about moisture under new raised floor
Here's what my builder was supposed to do with a similar situation - new living space built over an existing concrete slab for a garage.

1) Fill with crushed, well draining stone

2) Lay down  6 mil vapor barrier on top of the stone

3) Pour 4" concrete slab up to 1-1/2" below the level of the existing concrete block.

4) Install 2x8 floor joists

5) Insulate between the floor joists

6) Install subfloor

7) Install final flooring