Ok, so we need to come up with some of the questions. That will them prompt you. Don't ask the " are you prepared to.." Because he won't know, won't say, or will be negative. Ask for facts. V difficult to maintain credibility and refuse to give them. Will weigh against him. Make the assumption that you are splitting, not whether there is a whether in it, and it will become clearer and easier. Nothing will make it clearer that you are completely serious.
Eg
I shall need full disclosure from you, financial and otherwise. This is an initial list of questions but there will be more.
Financial
Assets, .
, property, in whose name is the house, approximate valuation for now. chattels, life insurances, investments, savings, cars, other property, debts owed to you. Pension
Liabilities, eg credit card debts, mortgages
Income, monthly, annual , bonus, dividends, interest, other income from property
Expenditure, mortgages , basic living cost, including food and transport to work, direct debits and standing orders, credit card interest and repayments, loans. School fees of any. Debts, eg gambling, membership of clubs plus approximate expenditure, this is not an exhaustive list, it will be for you to make full disclosure, not for me to have to ask the right questions.
I'll need all the paper work.
Other liabilities, of a personal kind, eg supporting anyone else, charitable payments
Details of current contract with employer, terms and conditions. Mortgage document, if any
I will pro provide on my part expenditure on the children. And costs of eg uniform, ordinary clothing, cost of school lunches. I will provide it on an annual and monthly basis in terms what I have spent, I will also provide what I think is reasonable to spend, which is higher. I shall also provide what is spent on non children housekeeping, again I shall divide into what I spend and what I would think reasonable which would allow for occasional treats,
The issues you will need to think about are
Where you work
The house
The level of contact you want
We will jointly need to agree on how we tell the children
Others, more experienced, may tell me this is bad tactics, but it's what I would do. Quite civilised, no blame, factual.