Also you said: “ H has completely unrealistic expectations of what a D is going to do to him (us) financially. This really concerns me because we have the potential to D amicably or collaboratively, but the only way he is going to avoid those huge consequences is if I walk away with nothing (totally unrealistic, not going to happen). So I worry that his lack of understanding is going to create huge conflict when he realizes the truth and he will blame it on me and things will get ugly. We have crossed this bridge a few times over the last 6 months where he has an unrealistic idea in his head of how things are going to unfold and then is shocked when they unfold according to common sense consequences. ”
Negotiating with him without the benefit of a lawyer telling him that what he expects is unreasonable and no judge in the land would give him that is unlikely to be helpful. I would have a private consultation with a divorce attorney - without letting your H know about it - and get a clear picture of what you can expect to get.
Also, give us some (general, non-identifying) information on the financials here and we can probably offer some advice. What kind of joint business is this? Is it a joint business because your name is on it for tax purposes or do/did you have a significant hand in building/running it? Does it have resale value? What job skills/qualifications do you have? What could you earn on your own? Does it make a lot of money or is it just barely paying the expenses of a single household and unlikely to cover the expenses of two? Are there assets, like equity in your home or equipment owned by the company? Are there employees? Do I remember correctly that there was something hunky about you being paid a salary even though you did little work as some kind of tax dodge?
Get copies of the business returns and your tax returns, the business accounts, statements on any retirement accounts or pensions, and bring that information with you to your attorneys visit.
Knowledge is power. And if the finances are not going to be enough to support two households, you need to start figuring out how to address that long term.
Most likely he wants to negotiate yourselves so he can cheat you out of what is rightfully yours. Find out your rights and where the money is.