I managed to replace the studs today. I tried removing the rotor to verify I'd be able use a hinged ball joint separator, but the rotor was frozen on there. I didn't have screws to push the rotor off the hub (or know what size they are). So I whacked the rotor with a rubber mallet, and then with a hammer, but no dice. And without the rotor off, a ball joint separator wasn't going to fit on the hub.
So I just whacked the broken studs with the hammer and they popped out the back. Honda didn't leave a hole or anything to allow the studs to pass through easily. But getting them out wasn't hard because since they were broken, they were short enough to maneuver past the splash guard. But that splash guard blocked access to getting the new ones in. Luckily, the splash guard is just thin stamped steel and no match for my hammer:
Then I was able to put the new studs in:
I used a wrench to more or less restore the splash guard to its former glory, and even added some black paint to protect the newly exposed metal from rust. To pull the studs through, Honda recommends using a bunch of 14mm washers to torque against. I didn't have any 14mm washers, but the hole in the end of this crescent wrench worked:
That did destroy the mating surface of the lug nut, but since I was replacing all the lug nuts I used one of the old ones. I used a torque wrench so I wouldn't go past 94 ft/lbs. Also, I used some brake grease between the crescent wrench and lug nut. And I had to keep applying new grease when it would torque out before the stud was all the way in.
After putting the wheel on I drove it a few miles and torqued it again. A bunch of the studs did tighten up more, I assume because I moved the rotor a little when I was whacking it earlier. After 50 miles or so I'll go around the car and do a final torque on all the wheels.