OP, you've had advice on what child maintenance you'd be entitled to as a minimum on a separate thread - you can easily double check on the child maintenance calculator on the amounts due, depending of nights with you. As the primary carer, this is something the children are entitled to have coming to cover their costs. They may be entitled to more, as you have indicated his income exceeds 100k net in earnings plus 40k+ in other income.
You may be entitled to some spousal maintenance, if so, likely time limited to help you back into the work place.
Please seek objective, legal advice re both maintenance and assets. You both need to declare everything, so if you have access to the details of all that each of you own, then that may come in useful. It is worth paying for proper advice, even if you have to approach your family to help you here. The assets you are entitled to is exactly that; and your children deserve for you to have all you should. This includes pensions as you were unable to accrue a pension whilst you looked after the children.
Either the inheritance is in your name, held for you in trust or not, if it is in your father's name - it is not yours. Please get legal advice on that too.
You will be entitled to child benefit. You currently are, by the way (he would need to deal with a balancing tax charge on his tax return). I hope you are currently at least claiming credits for NI purposes.
Depending on your savings, you may or may not be entitled to other benefits. If it's over 16k, probably not. But if you don't have much in savings, then check out entitledto to get an idea, it may surprise you if you are not expecting to earn a lot to start off with.
You can get some help with childcare if you are on your own. Your younger child is likely to be eligible for at least 15 hours childcare per week until at least reception age, and you may be eligible for tax free childcare. Check the sites out.