The R50 pathfinders and QX4's with the 3.3L engines came factory equipped with a special tool from Nissan to help remove that #6 spark plug.
The tool is supposed to be stored under the back seat, along with the jack.
I suspect after a few ownership changes and 15 years of driving, that some of these tools have disappeared.
Start by checking under the seat and see if the tool is still there.
If not, then maybe someone you know in your area with the same vintage R50 can lend you the tool when you need it.
Check out this earlier thread on the spark plug removal issue on the 3.3L engine.
Lots of good information here.
spark-plugs-due-for-change-t314373.html ... lug%20tool