Sorry ,to find about bad health of little one.
Well,since he showed no improvement even after taking azithromycin for 3 days so he should go to ER.
Yes,he might be having pneumonia.
Also as you told he is taking nothing by mouth.
So again it is worrying condition.
Also not sleeping at night as he cannot breath properly.
Infection is extensive.
Are you okay/
Are you giving any steam inhlation to him?
Try giving him steam.
Wheezing or crackles in chest of kids is alarming sign of increase in infection.
Nebulization or steam inhalation is must for his congestion.
RSV can cause troubled breathing,high fever,chest crackles ,worsening cough and dehydration.
But you know in even in RSV kids who have difficulty breathing and dehydration are admitted in hospital.