A.,
If it is not his ears or teething, it could just be that he is about to make a developmental leap. Both of mine would have boughts of restlessness at night--waking up a lot, crying--for as much as two weeks at a time, right before they made a big developmental jump. Whether it be speech or whatever. I think little nightmares can accompany this.
It also sounds like he is very aware, i.e. asking to go to bed and whatnot. He is probably figuring out that the world is a big place and he is pretty small. Totally normal. At 19 months he is a little sponge, taking in and processing all day long. At night when his brain tries to rest, he may just have some trouble adjusting to all his new developments.
I am guessing in a couple of weeks he will settle back down. As long as you remain calm and consistent (I know! Easier said than done at 2:00 in the morning!) he will get right back to his good sleeping patterns. This too shall pass!