I loved "Healthy Sleep Habits, Happy Child" by Marc Weissbluth.
I also had a large baby - she was actually even bigger than your little boy! She hit 19 lbs by four months. Part of the reason she was so tubby is that she had reflux and so she breastfed often, and I had quite the supply going on. She was nursing every two hours through the night at around five months of age (this was an improvement over her at about four months, before we put her on Zantac, when she would wake every hour to nurse to soothe her ouchy tummy between about two and seven AM.) So after five months of almost no sleep I was exhausted and realised that I needed to do something to get some sleep. I figured I could get by with three hour blocks, so we moved her from the co-sleeper to her crib in her own room, and if she woke up less than three hours after a nursing session I didn't go to her.
Yes, we had some nights with a significant amount of screaming. I would turn the monitor down so I couldn't really hear it too loud and often fell back asleep for a bit. Then when I woke up again after she'd settled down I'd turn the monitor back up so that I could hear when she next woke, and at that point it'd been long enough that I would go to her.
She dropped down to waking up about three times per night, and then two, then one, and finally night weaned at about 17 months of age. Of course, silly me managed to get pregnant with #2 when she was 13 months old, so I still wake up a few times per night because of my bladder - but at least this time I'm waking up because my body says to, not because she does! :)