How about removing the driver's side wheel, with a jack stand supporting the axle under the spring, then using a 6-point socket on a flex handle and some extensions from the wheel well? Once the plug is hot and lubed, it should turn right out with just a little effort. What size is the hex socket you're using? I have had some success with driving a slightly smaller metric socket over a rounded-off bolt head or nut, such as a 13 MM on a 9/16, etc.
Jerry
