Thank you for your query,
Night time sleep for 8.5 hours at a stretch is normal for a 6 months old baby and the naps will be divided with in between playing during the daytime.
you can give mucolytic
cough drops after consulting your doctor.
Intermittent rapid breathing is seen in infants during playing, excited mood but if it is continuous then it is concerning thing.
Consult your Pediatrician
in the morning and take proper meidcation advise.
Hope I have answered your query.