Memes - You may want to try pushing him to drop a nap. We transitioned DS to 2 naps at that age. He wasn't having nighttime sleep issues, but it did make him nap better (and allowed us some semblance of a schedule!).
RE: fussiness, my DS went through several fussy stages as an infant, and in my (somewhat hazy) memory, most were related to things he wanted to do but couldn't yet: sitting, crawling, etc. Could it be something like that? The reflux or teething are both likely culprits, too, of course. Hope you can figure it out and/or the phase passes!
Sorry for the bad sleep clc. Count me among the sleep-deprived today. DS has a cold and was coughing a ton last night. I wish we could bring ourselves to just switch off the monitor. We know he's fine, and if he woke up we'd hear him through the walls, but I just hate the thought of shutting it off so I can get a good sleep when his is clearly not that good :-(.