The furlough scheme is designed primarily to prevent companies from making staff redundant during closures. You are both keyworkers, so you are not in this position. It is intended to stop short-term job losses and make it possible for businesses to get up and running quickly when they're allowed to, and when they have orders/contracts to fulfill.
If you're both keyworkers, your school-age children should be eligible for a place at school. If you have younger children, and opted for your husband to work on a ZHC to save on childcare, which is perfectly reasonable, I'm afraid that that is what you are being "financially punished" for. ZHC's are always risky and you must have realised this when you decided to go down that route.
I can't believe that I'm sounding like I'm sticking up for the Tories (I despise them with every fibre of my being lol), but they can't come up with schemes that cover every single possible arrangement of family finances that might be affected by the various permutations of how Covid can affect people's finances. People's lives are too complex!
It's grim, I know, and you've been unlucky, but you took a risk and it hasn't paid off. Have you checked if you are now eligible for universal credit because your income has dropped? I know you might not get a lot, but if things are really tight, every little helps.
When do you think you'll be able to return home? I think incubation is only a couple of weeks, so hopefully it won't be for much.