Deaf Dog's Behavioural Problems

Can anyone help me with my 12yr old Cavalier King Charles Spaniel?
Since my Rottie died 13mths ago I have been having trouble with Jasper. We have always been close ( from the moment I rescued him at age 7 when he was already deaf) but now I cann't leave him at home, either alone or with my partner. He cries & barks all the time. I don't give him a lot of attention but he is in the house and around me a lot.

If I take him with me in the car I can leave him for hours. He will either sleep or look out of the window quite happily, but at home he cries.

Sometimes he will also use the house as a toilet when I go out.

Jasper does respond to sign language & is very obedient. But I am at a loss as to how to handle his separation anxiety.