I haven't the time to read all the thread, so going just by the opening post, I would say that you and your husband, with no mortgage or rent to pay, would manage perfectly well on his £18K and without any of your income at all. You would even have enough for a few luxuries.
As you seem to have substantial capital as well, there will be no problems about replacing household items that give up the ghost, or other sudden expernses. You will have that capital to fall back on when you need to pay for care, and also the value of your house.
If DH wants to know what you will need to cover your living costs, sit down with a sheet of paper ruled into several columns and write down, in the first column, a list of all the things you spend money on -
Mortgage/rent
Council tax
House and contents insurance
Personal insurance
Car repairs/maintenance/petrol
Car insurance
Electricity and gas
Holidays
Eating out
Groceries
Clothes and shoes
Christmas
and so on.
Then add the current cost of each in the second column.
In the third column write the absolute minimum for each that you could get by on if you really had to tighten your belt. Bear in mind that when neither of you commute to work, you will save a lot on travel costs (do you run two cars?) and you will not be wearing "work clothes"
Add up each column of figures.
Marvel at the difference! Then stop worrying about how you would manage.