Water leak around shut off under the floor, *See ic)

I'd suggest to first determine exactly what's leaking. Tissue paper positioned close to the pipes will help to determine that.

I'd suggest to use a Sharkbite valve/fitting combination for replacement. You will need to cut/grind those band clamps off the existing pipe to remove the valve. Removing the clamp with the phillips head fastener will probably help when working on this.