Could you quote the paragraph of TOS saying that please? Because as it has been explained before by several people, ToS don't prohibit it obviously. So the casino has obviously taken an illegal action against its own rules by doing that. If you open an account from the same residential or professional network as someone else you don't even know, your account would be banned and your funds locked while you have been not even aware of doing something that could be wrong in any way. This kind of rule would be totally unfair and abusive.
Few members already quoted the rule from ToS stating that multi-accounting is prohibited on Stake.
In fact, it's common sense. OP's husband made some huge wins and his account got limited. They created a new account to curcumvent this limitation and be able to place big bets again. So, it's normal if the second account or even both account will be banned for trying to cheat the system.