Okay I thought I might do an update. DS is now 21 months and has been sleeping through- mostly- since 18 months. We've now tried letting him self-settle. I was rather anxious about this. DS has been in a toddler bed and I figured that he would just jump out and come screaming down the hallway OR we would have a lot of tears (which I didn't want).
So the first night we tired DH took DS to bed, gave him a bottle and waited until he was done then said goodnight and left. No crying but he did "talk" for about 30 minutes before getting out of bed. DH then settled him within 10 minutes. Second night DH did the same routine but DS knew what was happening so he only waited 10 minutes before getting up. It took two goes for him to fall asleep. Then last night DH did the same routine again. DS talked for about 20 minutes and then it was quiet. DH and I waited with bated breath thinking this was too good to be true. DS self-settled for the first time EVER. I didn't think it was possible. We'll see what happens tonight!