What are your children doing/contributing to the household costs?
At 18 and 20, whilst they are still YOUR children, they are adults not children.
If they are earning they should be paying at the least a nominal amount of board.
If they are studying, can they get a part-time job to help fund their own driving lessons?
And they absolutely should be doing their fair share around the house!
It does sound like your H has possibly made some less than sound financial decisions e.g. why didn't they have pensions? Pensions are a really tax efficient allowable expense for small businesses!
Also from what you've written, your husband didnt LOSE his business, he was bought off for 50k, he didn't go bankrupt.
Whether that was a good deal or not, he had to agree to that settlement figure surely?
Did you take financial advice re: paying off the mortgage versus investing some into a pension?
Given your ages, you've both still got a good 15 years to add to a pension. Look at AVCs in your existing work pensions - if you dont have one, why not? Because you are eligible for auto enrollment into a workplace pension scheme. If either of you have opted out, it back in immediately because you are losing out on employers contributions and tax relief.
What does he say about his lack of pension?
I think from your H's perspective he probably feels like he's "bought" the right to work 3 days having paid off the mortgage? And presumably is still contributing to household expenses. If your combined incomes arent sufficient then you need to discuss together how to either optimise your incomes or reduce your outgoings.
In terms of sharing the load, have you discussed this with him? What does he do on his non working days? Is he supporting the teens?
I think you need to raise it with him because the resentment is festering. As a mum, youve worked AND carried the household labour for years, its not unreasonable to want him to take that load on now he is working part-time.