BS- have you got a oil burner? Tea tree oil or eucalyptus oil mixed with water helps to clean the nose. So does a little drop of warm water put up the nose- Just 1 drop at a time, it can help to moisten and loosen the yucky stuff blocking it. If you dont wnt to try that, put the shower on hot and close the door, the steam should help.
Part of his crying will be unable to breathe, he'll be scared on a very basic instinct level. My DS2 stil freaks out when he gets a cold and cant breathe.
Hugs to both of you, its so hard when they dont stop crying.