Well, you're just starting out in the process so you'll be very relieved when you meet with your solicitor next week! You are not expected to be Finance Expert in divorce - that's your solicitor's job to know (so make sure you get the right solicitor).
You need a Finance Specialist Divorce Solicitor (not a jack of all trades). So check they have done work in similar divorces to your own individual circumstances.
The family home is 'shared' but inheritance, depending on how long you were married, may play a feature. Sometimes it's ringfenced, sometimes it's not. A key thing is how it was used, and how long you were married.
That's why every divorce is different = every marriage is different. There a few hard and fast rules.
If you think of the value of the Business + the House + Any other assets (e.g. cars, jewellery, etc) - debts = pot to be split up between you, he and your children.
The think about what your needs are, what his needs are. Once the pot is divided are everyone's needs met? If not, how can they be? If they are, what is the surplus? How should that be divided?
Turnover does not value a business, for that you need to look on the balance sheet for its equity value. Same as a house. The value of a house to you (not to a buyer) is: Sales Value - Mortgage - Costs of Sale = Real worth. Don't worry if you don't have any of this. It can be obtained later on.
So if your parents put in 25,000 what paperwork (emails etc) do you have of the intention of that money. They too may have a claim on the business.
Take with you any evidence, or at least start collecting it, of the loans by your parents, your inheritance etc that supports your case. Don't worry if you haven't got it all by your first appointment, you'll have to get it done for your Form E (which is the book of your life), and an essential part of a litigated divorce (which yours is not right now).
He will have to supply all of his bank transactions if you have a litigated divorce, including his business ones.
You can argue anything you like - but it all comes down to agreeing a settlement. So you may argue to ringfence the inheritance, he may argue he wants to keep the business - if there's a big difference in the between the values of those, he may offer you a lump sum to balance it (or ownership of the house.
Divorce is a very big, very long argument. If you cannot resolve these between yourselves (via your solicitors) then you have no alternative but to go to court. But, it's a very stressful difficult time. Good luck with it.
(And remember, anything "he says" should be taken with a pinch of salt).