It's good to be careful. But I think you are kid gloving this a little too much. Be 100% sure you have the correct size socket and that it is fully engaged on the plug and that it is nice and square. Get the correct length extension so that you can get good leverage on the wrench and pull nice and square and in a flat plane. Make sure you are pulling counter clockwise. Then just apply whatever pressure is necessary to break it loose.

If you do all that and still have problems then someone cross-threaded the plug into the head at the factory or something.