It looks like the ground wire in the trunk is supposed to be held on with a nut. There's no nut there. I haven't checked the front of the car yet.
Those grounds are all over the car! I think there is something like 20 or so, if you count the light grounds, the ones under the dash, etc.
I've been scratching my head the last day, trying to figure out what might be going on with your lights on the car. I remembered I had a similar problem (car would not start with lights OFF).
Do you know that big bundle of wires that sits behind the fuse box, and in front of the firewall? The one with all the bullet connectors, and might have a couple of in-line fuses (if someone didn't mess with your harness)? Check those connectors, and make sure they are all seated really good. I think there are a few that run down to the starter from that bundle, too. I would pull them all apart, and twist them to make sure they are seated really good.
They make a special little brush to clean those male and female ends of those connectors. I need to get one, or see if I can find a Dremel brush that will work.