There were so many signs that this was not the right time to start a new business adventure.
1. "We have 2 small children and have tons of expenses" - so you are not in any position to be able to support a new business, as a lot of capital investment would be required, and you have little to spare now.
2. Even though you two agreed it was "just to get an idea and maybe look at starting something up in the next couple of years" he went ahead and "paid the deposit with his own funds" even though you would be required to put in 40%? So he did that without consulting you, even though this affects the both of you, and your family? In spite of the fact that you are "going to bear the burden of the household expenses till his business starts making money"? That shows a lack of ability to consider all the factors, not a good sign in a business man.
3. You are going to have to use your savings both to support the business and keep yourselves going. What happens if they run out? Does he have a contingency plan? After all you "have no equity in our home right now and i suffered a huge loss in monthly income".
4. Then there's his general attitude - "he really has not progressed a whole lot in his life (he's a very laid back person) i do not have 100% confidence that he will succeed." So what if it gets in the "too hard" basket? Where will that leave your family?
Sorry it doesn't look like he has the resources or the right attitude to make a go of it. But since the money has already been spent, you are going to have to push him hard to make a go of it, which he may come to resent you for.