OP I am sorry you are in such a difficult and unhappy situation,
I’m not sure how soon you will receive the money but to begin with I would ‘park’ it safely.
Which is £20k in an ISA
£50k in premium bonds
The rest in high interest savings accounts: look on MSE for the best rates. Do not put more than £85k in each account.
Reasons: Any interest you earn over £1k is taxed, except for interest in an ISA, and Premium Bond winnings are not taxed.
Money up to £85k in any one bank is safe if that bank collapses.
Do not put one penny in a joint account and for now do not spend one penny of it on your shared house or on a shared holiday, or even household food/ bills
Talk to a solicitor about where you stand, including confirming how to ring fence your inheritance. Because I think it is the case that an inheritance is not seen as a ‘marital asset’ as long as none has been use for your joint family benefit or been put in a joint account
I would see a solicitor before you receive the money , and have an account in your sole name open ready for the money to go into.
Then talk about divorce. Find out from the solicitor what your prospects would be, financially. How much equity from the house you would get etc. Go with as many details you know of your H’s financial situation. Does he have a pension / savings etc.
Also take all your own details: do you have any savings, pension, will you get a state pension, your stake in your Mum’s flat etc.
Then talk to a pensions advisor.
These are all practical steps to protect you and gain knowledge.
Because really your most important decision is how would you like to live and how can you do it. Do you want to live free from your H and divorce ? How will you live if you divorce? How will you live if you cannot work? How can you best get better and recover from being unwell?
Then use the money in the best way to support your mental health and future happiness.