@rdsh - replying to this in response to the joint finances question, but I have read all of your posts.
Joint finances don't have to mean fully joint - but family expenses should absolutely be joint.
Next time DH suggests selling the flat - tell him you will consider it, but only if you sit down together and go through the household budget and look at how it be shared.
That means all household bills, mortgage, flat maintenance and fees, childcare expenses, food, childrens activity, clothes etc, income (wages and rental etc) and savings and debt (but only jointly accrued debts) - also a fair contribution to pensions and retirement savings.
When you are looking at income / expenditure you need to account for the childcare element - so if you were working full time and therefore bringing in a similar monthly income to DH, how much extra would it cost in childcare - that essentially goes onto your income / contribution.
If you want to keep some element of separate finances, you then need to work out proportionately how much you should both contribute to cover those bills / debts and whatever is left from your incomes after that is for you to do what you want with.
For the debts you can look at all options - is the interest terrible or liveable with a clear end date. Can you consolidate, use 0% credit cards etc? If none of that is an option and the debt will just keep increasing, then you may need to look at selling assets or reducing the debt in other ways (different car etc).
Do NOT allow all of the children's expenses to be lumped as your personal expenses - that way madness lies!
But whether DH agrees to doing that or simply shuts up about selling the flat you really do need to get to grips a lot more with your household finances - partly because of a risk around any future split, but also because if, god forbid, something happened to DH you don't want any nasty surprises!
Having helped relatives who have lost their spouses sort out finances when they had no idea what was going on, it is an absolute nightmare to try and do at a very emotional time. If you have a good idea about your household finances, it is one less stress!