FDR - How much of the share

I have a long winded Divorce ahead and there is a lot of financial dispute.

I was married 12 years and plus another 3 years still in the marital home whilst Divorce case has been going on since 2017.
We have 2 children together, 5 and 13.

Ex does not want the children and is happy for them to remain with me.
Can i request for 80% share from the divorce as a starting point as he will be entitled to his fathers will, where he will gain a considerate amount of wealth?

My career stopped after the birth of my first child, and him and his family did not allow me to work or continue with my career.
I am not in the position to go out and get retrained or attend courses as once we move out of the marital home (which belongs to his parents) I will not be living in close proximity to friends or family that would be able to help with the kids. Also, to point out, my youngest child has severe food allergies and a strict care plan.

Since the ex has no other responsibilities, can i ask for a larger share of his assets so that my children are looked after and according to the lifestyle that they have always had?

I would like to be more prepared for my court date than what i already am. My financial circumstances at the moment are not great as i have spent a lot of money of solicitors and not got anywhere. For now i have been representing myself, hence why the lack of knowledge.

What your husband may or may not stand to inherit in the future is irrelevant. A court will not take into account the possibility of a future inheritance because it is too uncertain to be quantified and in any case his parents are not obliged to leave him anything.

It is impossible to say whether you can reasonably ask for 80% of all assets because you do not say what they are or attribute any value to such a share. Say, for instance, a couple had total assets worth £20 million. Would it be reasonable for one spouse in that case to receive £16 million and the other £4 million? Almost certainly not because £10 million would almost certainly provide adequately for both. Similarly if the assets were worth, say, £400,000 in total. Awarding £320,000 to one and £80,000 to the other could well be unfair if £80,000 did not meet that spouse's reasonable needs. The fact is that figures matter. Percentages on their own are meaningless.

As to keeping the lifestyle you have always had the fact is that is rarely possible because after divorce the same assets and income need to support two households rather than one. For most people that involves some drop in standard of living. It is not the case that the standard of living of one spouse must be preserved at the expense of the other.