Hurray for cosleeping with your son! I am also the only one in the family who cosleeps, nursing beyond 12 months, etc, and loving it. My SIL had her DD CIO to train her to sleep in her crib and DD cried so much that she fell out(? off?) of it somehow at 6 months. Very heartbreaking.
I am no expert in childrearing since I only have one child. However, your son sounds exactly like my DD at that age. She could be deep asleep, and as soon as I put her down in her crib, she woke up. After a while, I got so tired of repeating it over and over (since I also had to nurse her again), and I needed sleep. Luckily, my DH had more time to stay home to hold her while she slept. We did that until DD was 5 months when I finally decided to just nurse her in bed and start cosleeping. She is still not the best sleeper. Often times, I cannot get out of bed because she wakes up if I don't choose the right timing. But cosleeping and nursing in bed were the best decisions I have made. She loves being close to me and I feel better knowing that I can give her what she needs right away.