Well, You did not mention where your house was located, but usually your floor slab to foundation wall detail is typical of a well designed basement. The slab rests on top of the footing with an expansion joint between the edge of the slab and the foundation wall. This keeps the expansion and contraction of the floor slab from putting undo pressure on your foundation (basement) wall. If you did not have this, you could get some severe cracks in the wall..........you do not want this.
Perimeter water (and under slab water) usually taken in by a perimeter drainage system. If you have a drain tile on each side of the footing, your water problems should be minimal. Of course, this depends on where your house is situated. If you do not have a perimeter drainage system, and your house has had no history of water problems, you are probably ok. However, if your house is new, and no perimeter drainage system, you "could" have problems. You should then ask your builder if he installed the system. Your options would then be discussed with your builder. Let us know.
As far as radon.........you have me there.I am not an expert in this problem cuz' I live in an area that has a very minor issue with this problem. I know that there can be a uder slab venting system (PVC) that relieves the pressure to the outside. Could be you would find info on the web or some of the other quite helpful soles who frequent this site. I am in and out but I hope I have put some light on your situation.