Getting rid of one of the naps can actually backfire on you. The more tired he is the more of a bear he is going to be. You can experiment with it but he's going thru a lot right now and needs rest. Sleep begets sleep.
At around 12 months babies who have been sleeping well will sometimes have major sleep disruptions because they become much more aware of the world around, wake in the night and don't want to miss out. It's much harder for your little man because he wakes and comfort (aka mom and dad) are right there.
When my son was teething I never had a clue but my daughter was miserable. I couldn't even begin to imagine trying to make her cry it out while she was going thru that (well, ever for that matter when there are kind and gentle ways to *teach* baby how to sleep)
Leaving him to cry it out won't solve the things that are probably going on with him-sounds like he's caught in a cycle of exhaustion, he's teething and that is very tough on little ones who don't understand the pain, he's at the age where he is becoming very aware of the world around him.
You don't say if you are nursing but know that many babies don't sleep all night till they are fully weaned. My son was able to be a champ sleeper, my daughter didn't always sleep all night till she was weaned at 20 months. Different kids, different night needs.
Why not check out Dr. Sears Baby Sleep book (there is section on toddlers), The Baby Whisperer and The No-Cry Sleep Solution? THey all have invaluable tips and tricks to help you formulate a sleep plan to help him get more rest. I gleaned info from all 3 to come up with sleep plans for both of mine and they are both fantastic sleepers now.
Once you get a game plan, why not let big sister sleep in your room and let the little one start sleeping in the other room while you are teaching/helping him learn to settle/sleep better at night.
And lastly, if he was doing pretty well, try to get him rested again by sticking to his nap routine and the bed routines he knows and depends on and this bump will pass. Remember, infant sleep is never static. Illness, fatigue, growing pains, teething, night terrors, milestones will all causes bumps in the road.