Small thing but VHI looks a bit low and you are incurring medical expenses, maybe worth stepping up. Is that life assurance expensive?
If one partner is accumulating huge savings in secret that is unacceptable and "being at peace" with it is doing yourself a disservice. (Note, not saying this applies here as I havent deciphered how much the difference was when you said you updated "there was more savings than expected").
While husband might want a separate account there ultimately needs to be some transparency given huge outgoings revolve around kids and mortgage - joint responsibility. There is of course a spectrum from sharing accounts and counting pennies together, to not sharing accounts and every detail. We have separate accounts, only recently got a joint account because revolut app makes it so easy to gain visibilty and move money from own accounts to joint account. But long story short - not knowing other half's exact finances are one thing, being 1000s and 1000s of euros out is - in my opinion - a form of domestic abuse given the huge responsibility that is managing cashflow and pension building for a large family.
I realise that sounds very blunt - and worth repeating there is no need for joint accounts or micromanaging a partner but there is joint responsibility to ensure mortgage, pensions, and kids are serviced fairly. There are some basic minimum levels of transparency required to run a household cash flow - you should not be deprived of that.