annsixty, from your comment:
'I do not feel strong enough mentally to make drastic changes but must do something, anything, to make my life easier and less stressful.'
- looks incompatible with moving house right now. You say your DGD and S can't move on at the moment either.
You could divide the house into separate areas for each person - not physically with walls/doors - but each of you could occupy some rooms and take responsibility for them - keeping out of others - with perhaps a shared living room. That way, you're only responsible for your part.
You could also divide tasks e.g. your son could hoover and clean the floors, your DGD could shop and cook. I assume they pay 'rent', probably not much, so it's only fair that they work in the house as well. Still, keep trying to find a cleaner.
My neighbour always had student au-pairs when her son was growing up. When he left, she continued that arrangement, now calling them 'housekeepers', yet still for a small 'wage', a room and food. Perhaps that might suit you?