Cavalier King Charles Spaniels

Hi my name is Debbie,
I rescued a tricolour cavalier some 4 years ago, he started developing some strange behaviours scratching coughing and hypersensitivity to touch. I had a sleepless night with him last night as I was worried sick for him. I visited my vets first thing this morning I was informed that he had been assessed and has a level 3 heart murmur, and has the symptoms of Syringohydromgelia.
He has been given a shot of pain relief and a course of treatment.
He seems to want to hide all the time and lets out these horrendous screeches when he is just sitting or laying on the floor. Can any one give advice regarding this
cheers Debbie