Both of the concerns that I raised above are now kind-of addressed.
Regarding the difficulty removing the safety pin: I first tried a 13mm wrench to pull the pin, which did work but was still awkward (a wrench with a more angled head would help). But I changed my mind and instead removed the safety pin (easily done, with no tools). That makes it super easy to put the rack on AND take it off. It's not as secure, but for short trips it should be fine - the low central blue handle lets you get the rack really tight in to the receiver, and then you just press the button to lock it in. If I just remember to rock the rack as I tighten, I am not worried about our regular trips around town. If we are going to take a long trip where it will get a lot more jostling, I'll put the safety pin on for that trip (which should be no big deal since we take my wife's Model X on long trips, and it has an exposed receiver so the pin will be easy to access by hand).
Regarding the arm not folding flat when the tire grip is anywhere but at the top: I moved the rear tire grip all the way back up, so it now rests on the fender rather than the tire. I am a little concerned about damaging the fender, but I'll give it a try - I am at least confident the bike's not going to fall out or anything. The rack now folds up nicely all the way for storage and to stay neat and close against the car.
Here is what the rack looks like when it's mounted on the car, empty and stowed in the "storage" position up close to the car. Unfortunately the hatch will not open with the rack in this position:
Here is the rack in the same position, viewed from the side. Note that there is very little clearance...in fact if you really push the rack all the way in and fold it all the way up like this, the rack barely touches the black plastic part of the car. You don't have to push the rack in that far, though.
If you want to be able to open the hatch, you can leave the rack in the "halfway" position. It sticks out a little further from the car, but it's still closer than some other racks I have had:
Here's what it looks like with a bike on the rack:
From a lower vantage point, you can see that there's a lot of clearance so your bike and the rack are unlikely to drag on anything:
Here is the clearance between the bike's pedals and the car:
If you have the rack in the "halfway" position so you can open the hatch, and you want to remove the pin securing the rack to the receiver, you can give yourself slightly easier access by opening the hatch and then folding up half of the tray:
