I've had several, everyone has turned around nicely within a few days. Chameleons take a long time to heal but generally after 3-5 days on meds you notice a big improvement and it'll finally disapear a few weeks later. Little Pascal will start breathing easier after a couple days of meds, you'll see. You can (if you haven't done so already) raise his basking spot temp a little bit so that it works to kick up his metabolism and fight the infection faster. Something like 3-5 degrees is enough, you don't have to roast him.
I have a Meller's who came to me with a pretty severe RI, you could hear her gurgle and rasp as she breathed from across the room. 3 days into her antibiotic the sounds were gone and she was breathing much better.