The red discharge you mention is called Porphyrin and is usually nothing to worry about unless it's excessive. What are you keeping him on? Wood chip/sawdust is never a good thing for rats as it can aggravate the nasal passages and cause sneezing. A substrate like Bio-Catolet or Carefresh is best for rats.

Also, rats often sneeze when they're anxious, and as you've only had your rat 2 weeks, it could just be that he needs a little longer to settle in, or, yes, it could be that the air freshener is causing him to sneeze if his cage is near to it.

But the thing to really listen for is any rustling on his chest, which could indicate Myco/chest infection which would require Baytril (an antibiotic) to help clear.