So the area at the top of the wall should be sealed somewhat as a fire stop.
What is done here is The plate on top of the conrete is 2x6 and we add 2 2x4s. One tight against the original plate and one tight to that. That is the top plate of the wall and with a eight inch foundation you new wall i one inch away from the concrete wall. That should get you far enough away to clear any bumps in the wall, although sometime we have to skinny a stud to get clearence.
Using this method and if the upstairs is sq. so is the basement Just level down from the top plate to the floor to set the bottom plate.
I would leave the concrete lumps there, build the rest of the walls that have no lumps then in that section raise your bottom plate 3 1/2 inches and built that wall. You can then cut a 45* off the side of a 2x4 and place it under the bottom plate. Then pin a treated peice to the concrete wall right beside a stud so you can find plumb for the wall and tag it to the block on the wall.