WorriedDIL It's going to be up to you to be the strong one and being tough with this old despot is what he needs.
Clearly he has waltzed through life getting his own rude way for far too long.
He has a right to his opinion but in your home you have the right to tell him to keep his wretched opinions to himself.
And warn him if he doesn't, you'll give him bus fare home tout de suite
Your DH says he feels his mother would want you to look after him but I'd like to bet that such a wonderful lady would not want her son's care for his father to result in ruining your lives.
Work out a calm but definite set of behaviour rules whilst he is enjoying your generosity and your home and put it to him with firmness.
If you feel your husband is up to it, consult him but I feel that in the end, it's you who must be the guardian angel and put this old rogue in his place.
I'll tell you something, WorriedDIL if he visited with me, his first rude comment might be ignored; his second would see him on the other side of the door, carrying his suitcase! 
Please help! (grandchild being locked in bedroom)


good luck