I think I know the kind of bator you are talking about, I think my mom had one years ago, it is the first kind I remember her using. I wonder if the wafer thermostat needs to be replaced? I think she had to do that with hers once(or maybe that's when she got a new incubator? Not sure which.).
I know you are on a limited timeframe, with lockdown for the first eggs coming in about 4 days, but could you see about getting a new wafer for your old bator?
If not, then I am not sure about the turning of the second set while the first set is hatching.
I think I have read the main problem for the later hatching eggs(staggered hatch or not) is that they get kicked around by the earlier hatchlings, and sometimes get injured or killed from that. I think if you are not able to get the other bator figured out(and I would definitely keep trying it until "lockdown" time for the first set), I would put the second set in an egg carton(inside the bator of course, I think people cut the bottoms out of them, to help with air circulation, a paper type verses styrofoam would probably be better); to prevent them getting used as kickballs while the others hatch. As far as turning the second set; I am not sure. I have read on byc about some people who do not turn eggs at all after the point they are free swimming on their own, but you might read up on that, and see if you are comfortable with that. I would probably bite the bullet; put the eggs in a carton, pointy side down, and prop one side up, and instead of turning, switch which side is propped up; and just really watch the humidity to make sure it stays where it needs to be. There is another person on here who regularly does staggered hatches, you might try to search for that, "staggered hatches", and see what info you can get, maybe contact that person?
Hope that helps, maybe some others can chime in with better advice. Sure hope your hatch goes great!
Carrie