I think your DH is grieving. Things can seem stark, definite and a sense of 'emotional truth' can be unusually powerful. It can be hard to recognise that this is because of emotions that are not just heightened, or unusually accessible but in part peculiar to the grieving process. His feelings and ideas are likely to change, given six months or a year.
I also think he is behaving like someone much richer than he is. This kind of largesse is for billionaires but, because he's never been any sort of 'rich' before, he can't tell the difference between very different shades of wealth.
In your position I'd ask if he would wait a year, then make a decision. He's grieving, he doesn't have to do everything at once now. It's a good idea to give himself some time, space and care, pace himself and not feel rushed.
In the meantime, I'd be putting together some financial facts and proposals. Paying off your mortgage would release revenue monthly and give you a real security and freedom - life changing in the context of an 'ordinary' life.
In particular, I find it mad that anyone would pay mortgage interest if they didn't have to - that's giving away money, to a bank, for nothing tangible in return. Why pay many thousands more than house is worth, servicing a debt, when you could choose to keep all your income to spend on real things? The 'charitable beneficiary' there is the bank (yes I know their charges are legit but it feels like giving money away and is if you don't have to). Pay the interest to a charity instead if you like AND you own the house.
Then get some quotes for repairs. They may be substantial. Get your house valued, as is, versus in good condition.
His conscience is strong, he's right that others are worse off. It's great that he'd like to help. He can. But, doing so driven by grief, guilt and without concern for his family and relationships - at a time when he doesn't have quiet mental space available to evaluate the consequences - is not a sensible idea.