When all was well he contributed 50% £, dadded well - but wasn't a fan of doing the house stuff, so you both got into the habit of his stuff / your stuff and it kind of worked.
He became seriously ill nearly a year ago so quite rightly got a pass then - but has been fit and well 7 months ... and he's still clutching the pass.
He's taking medical retirement, not because he's in poor health - he's fit enough to do the DIY he likes doing - but because it made admin sense to the business.
As in - he's perfectly capable of playing his part in the home. He just doesn't. The old habit trudges on.
Now you're feeling rock bottom because you're sick at the moment on top of being knackered, while he's back in good health - and lounging about enjoying himself. And still expecting you to do all the housework / wifework / mumwork on top of the only paid work. A spot of DIY really doesn't balance it all up.
Anger, sadness and resentment are absolutely understandably building - which isn't healthy for you two or the kids.
Work out exactly what it takes to run the household. Think of it like a business. Each task that needs to happen for the results you want. And include every hour you spend commuting and working. Maybe do a one week 24 hour plan that illustrates exactly what you did hour by hour.
Have the conversation.
Show him and tell him 'These are all the things I have to do every day to keep our home and family afloat.
I'm exhausted.
I can't cope any more.
I need help.'
It may be some of that lump sum could be used to get regular help if he cannot or will not step up and husband / dad.
A cleaner, shopping delivery, prepped food boxes, laundry service, dog walker, gardener, window cleaner etc etc.
It's a pressure cooker, and the pressure needs reducing now. Or he'll sink further and further into solidified habits and role model an unfair workload to the children.