Hi A.! Oooh sleep training is so hard and emotional, it brings out the "i know best" in everyone :) Anyhoo, here's my two cents. I did this with my daughter when she was about the same age as your son, and it took about 3 weeks for it to work, and since then we have not had any problems whatsoever (she is now 16 months). I kind of made up my own "rules" so to speak for her evening schedule, stuck to it, and as hard as it was, i just made myself not waver from it. My daughter figured out what was going on after about 4 nights, and for the next 10 or so it was really just making the message stick.
here's what i did:
5pm: dinner
5:30 bath
6pm: play quietly in her room, read a book
6:45: bedtime! (i know it's early, i moved it up from 7:30, and that extra 45 min made a HUGE difference. a lot of times when babies wake up a lot at night, it's bc they are just too tired, and they can't settle themselves long enough to sleep. it's weird, but it's TRUE. 8:30 might be too late for your little one to go to bed.)
- she would normally sleep for about 4 hours, and then wake up every few hours after that, when she went through a sleep cycle and coudln't resettle.
-i'd let her cry about 10-15 min, then go in, settle her down, cover her with kisses, and leave. i tried not to talk at all. I don't have anything against crying, but I wanted her to learn that yes, mommy will check on you, but that's it.
-if she was still crying, or started again, i'd let her go 20 min before going in. etc.
-I also started giving her a lovey and a pacifier (i know i know pacifiers are bad etc etc etc whatever, they work) at night, and that made a big difference right away. i'd sing her a song while she held her lovey and sucked on her paci, and tried to show her that when mommy isn't here, these things can help you. She now loves that lovey, and we use it and pacifier only for bedtime.
-i was nursing at the time, and i don't know if you are still nursing or bottlefeeding at night, but i cut that out at this time also (on the advice of my pediatrician, my daughter was at a very healthy size) and fed her a little extra at dinner.
-i learned that every night was going to be different, some were bigger fights than others, but I just held firm and stuck to my "rules". extended periods of crying didn't make a difference to my daughter, so I gave in and realized that she just needed to know that i was there, she was okay, and she could learn to do this. She definitely had nights where she regressed, and it got worse before it gets better.
Like i said, it took about 2-3 weeks to get the routine down and for her to sleep through the night. Babies that age should be sleeping about 12 hours each night. Any less than that and they are sleep-deprived and actually sleep worse (unlike adults). Try moving his bedtime earlier and stay consistent, and you'll be okay.
teething may also be a problem- Motrin helped a LOT for that. :)