Taking legal advice from your separated husband - a mug's game.
Twisting legal advice as one rule for women, another for man: discrimination. There is a whole other set of laws about that.
Believing the higher earner has all the power, and the lower earner is 'supplicant' - a very common mistake made by divorcing spouses.
There is no fixed way of determining settlement, the starting point is 50/50 but rarely is the finishing point 50/50 - everyone's divorce is unique because everyone's set up is different.
Factors which influence are:
Age and earning capacity of the adults
Age of the children
Where the children are to live
Family income and assets, debts and liabilities
Lifestyle enjoyed in the marriage
Length of marriage
Disability/Health
A starting point will look at what you 'need' and what he 'needs'. After that, what can be afforded. For most people, running two family homes out of one income cannot be afforded. A 'Mesher' Order, forcing the primary carer to stay in the marital home is often preferred by judges because the divorce is between the adults, not the children, and it minimises the damage to the children. However, staying in the family home 'because I want it to be my pension' won't cut it for anyone. This is about separating the marital assets (no matter who paid for them) in a fair manner.
He is entitled to 50%, and with his on-going life-limiting illness, he is going to be treated as a poorly person by the legal system. However, there are the needs of a very young person to balance against this.
Your needs will come third, I'm afraid - less alone you wants.
Yours is a complicated situation and your outcome will come down to what you negotiate. A solicitor will tell you what a judge might order, if you can't agree between yourselves. The onus is to agree between yourselves not rely on the court system to sort it out for you.
Sensible legal advice, even though it is cost ££££s will save you a helluva lot more in the long run, most likely.
Unfortunately, like a lot of earning spouses you cannot decide what he will get because you have the earnings. It, unfortunately, is all about needs and fairness. There are some on this thread who are trying to apply the laws because of he's role in society as 'man'. The rules are the same irrespective of gender. He may be the biggest twat in the world - but he remains a twat with rights. You remain the person with responsibilities. It might not feel 'fair' to you, but the law is impartial.
Depending on what you earn, paying him 1500 month may be the bargain of the century. It comes down to whether you can afford it. Until you have negotiated and agreed a financial order, that is a solution for having him out of the house. He could take you to court for that 1500 a month anyway, so all the better to agree to it if you can afford it.
It's the same laws for billionnaires as it is for the lowly poor person, I'm afraid. Fairness is only a point of view.