Thanks very much for all the information - didn't think of weighing the vehicle without the trailer, to get an idea of the weight of my junk. And thanks also for the hint about CAT scales - I had no idea how to find a scale to weigh vehicle and trailer. Turns out there's one at a truck stop not far from me, so all I have to do is talk to them about it.
I was a little surprised about the 1050 CCC (not 1020, I was typing from memory earlier). If I understand things, the hitch and tongue weight are part of the vehicle's load, so less than half of 1050 will be for passengers and junk, so around 400 lbs. I think I can make it under that but it will be close (100 lbs for clothes, another 50 for photo gear, 50-100 for general junk, leaving only 50 lbs unaccounted for - I definitely need to pack the JGC and get to a scale!). But I'm feeling more confident that the 1685 will work for me.
Thanks again for helping me to break things down like this. It looks like I'll need to think about everything the same way I did when I once tried backpacking - weight is everything! And there's a number of ways to lighten one's load (or not).
To continue showing my lack of knowledge - I looked at a couple of WD hitches online (the Reese dual cam and one of the Equal-i-zers), checking on weight and cost. They aren't exactly light (like 80 lbs) and I've never seen one in person. Are they all one piece? I'm going to be doing everything alone and I don't think I could manage to lift something that heavy.