Hi J.,
"They" say that 18 months is the earliest to start potty training a child but to tell you the truth, we have been working with our son since he was about 4 months old (when he could push enough with his feet to stand with us holding him.)
At that time, you know how they always pee when you open their diaper? Well at first I would just wait to catch it with a washcloth before putting on a new diaper. But then when he could stand, it was just an easy transition to stand him and let him pee in the sink (our changing table was in our 2nd bathroom) and then my husband had the idea around 4 or 5 months to hold him over the toilet to just give him the opportunity to poo also. We would only do this in the morning...
Now, my son is 16 months old and we have been practicing sitting on the potty together every morning since he was about 11 months old. We just give him an opportunity to use it when he wakes up in the morning and Voila! most of the time he takes us up on it to make his poo there. We only rarely (knock on wood!) have to deal with poopy diapers any more. It is soooooo nice. But again, we are not trying to force the issue, or mandate it, just encourage it. He seems to understand the concept and only in the last week has he started to use the sign for poopy and pee pee (we use the sign "dirty" for a poopy and "toilet" for a pee pee). He also has just started to try to say the words. It is interesting to watch because it shows that he knows what they mean... but he still hasnt' gotten to the point exactly where he knows WHEN they are coming and can tell me that yet.
With regards to peeing on the floor, ah the joys of boys! I was always jealous of boys abilities to do that as a kid :) but seriously. Maybe I am wierd but since I don't want to have to clean it up, I try to only give him "naked boy time" for a few minutes after I KNOW that he has made a pee pee. But even then we have had our accidents. You have to just laugh. My son always looks a little surprised and curious when it comes out. Just last night he peed in the hallway near our upstairs. I didn't say anything about it but just asked him if he was making a pee pee and then we told him that usually we do that in the toilet (and pointed) and then I handed him a towel and he tried to mop it up himself (I helped!) Things will click in as they do. I would just consider what structures you have in place to ENCOURAGE HIM and then adapt and be patient. Trust that he will learn in time and try to set a good example. Don't get all bent out of shape//stressed out about it when you approach it with him since kids pick up on those things and that's how "complexes" are born and stick with us later in life. Cheers!
PS regarding sleeping through the night - are you still nursing him? My boy didn't sleep entirely through the night until I stopped nursing him at night. Which literally took me getting up and supplementing boob with either water or serious food if he was really hungry at 4am for a couple weeks. And then all of the sudden boom! He was sleeping through the night. Now, he seems to stir and wake and cry only if he was worried about something before he went to sleep (maybe it comes back as a nightmare to wake him up?) But if the going to sleep process was generally gentle and enjoyable and he is very tired, he will usually go to bed and not wake up for a at least 8-10 hours... I also think that every child is different and some have different tolerances for noise. We weren't very "super quiet" when he was a baby and sleeping so now, if he is tired, he can fall asleep with noise around him. Others have created these ultra-quiet dead zones but then I notice their children wake up when they hear a pin drop. Just some thoughts! That is a tough one. I like other mothers suggestions of toys that he can entertain himself and making sure he is comfortable in the room. Our son when he wakes up pads around the room and plays with toys and looks out the window and only bugs us if he is disturbed or wanting something.