Seriously though... this is what I would do:
To kill the spider, you must understand the spider. What is your enemies primary motivation?
Food.
You need to draw him out. Tonight after it gets dark, leave your porch light on and catch a moth or some other small, fluttering insect. Put the sacrificial "lamb" in a small cup, go out to your 4Runner with a flashlight, and shake it out of the cup and into the web.
You have officially put a fresh kill at the entrance to the lion's den.
Stand back and watch as the spider emerges from its hiding place to feast. You will of course be standing by with some bug spray. As soon as he clears the dash by a few inches you nail him with the poison. The spider will probably attempt a hasty retreat once you blast him, so you'll have to have some way to knock him off the web quickly, or you'll have a spider corpse hidden up under the dash. I suggest a fly swatter, but a nice sturdy stick will work too.
Once you've got him off the web, you can watch sadistically as he writhes in agony and dies.
The end.
(PS... a video of the event would be most entertaining, I'm sure.)