OP good luck with the conversation, even after your updates, I think he is still taking the mickey. You don’t pay for living expenses in Uni if you don’t have an income (or better said, you find a job that helps to support them)
Mesher orders... keeping an interest in the equity of the house, is an arrangement that ends when the younger kid turns 18 or leaves FT secondary education. I would say that in the vast majority of the cases, the person staying in the house takes on the mortgage, unless there is a huge disparity on salaries with the non resident parent having the higher one, such order can be easily amended if the non resident parent has no longer funds to pay the mortgage.
With regards to the start up, is worth nothing unless is producing a sizeable amount of money, and no matter how much you are indirectly investing on it (like keeping your husband financially able/ comfortable while he is setting it up) it does NOT belong in any part or percentage to you if it is not written down in a contract. (I learn that the hard way, my ex’s start up was worth a few millions a couple of years after setting up, so it was “our business, our pension, our security” but the moment we split, my solicitor explained to me that despite the huge sacrifices I made, I had no right to a penny of it.
I would thread carefully Op, you never get to know your partner until you say “no” to something important to him. If you own a house, I wouldn’t be surprised if he claims the vast majority of the house equity on the very reasonable excuse, that all housewives use, that you had a better salary therefore they need to take more of the assets to achieve a fair split.
Good luck.