A couple of things you said confuse me.
What are 'good sleep habits'? I mean, I prefer to sleep with my husband, and have no intention of transitioning into my own bed so I can have whatever those are... I also cuddle up to him in the night, which so far (24 years now) hasn't proved to be a problem. He's in the military, so when he's gone I 'get' to sleep alone, and frankly it sucks. I'm not sure what I'd feel about myself and my marriage if my husband was in a big hurry to make sure we were sleeping separately...
You may find that if you cut back on the cereal and other solid foods during the day that your son nurses less in the night. It is not a well-known fact that breastmilk is very high in calories and fat and nutrients, particuarly toward the end of the day (milk tends to be waterier early on), making it tremendously more satisfying than the fat-free and nearly nutrition-free 'other choices' (unless you're feeding avocado or prime steak). Cereal, particularly, is extremely low in calories and nutrients, to the point where it fills babies up without giving them much in the way of food, so they end up hungrier, rather than more satisified, later. Kind of like using artificial sweeteners to satisfy a sweet-tooth: whatever the sweet tooth is looking for, the artificial sugars don't have, so people end up consuming a great deal more simple sugars following diet soda than they do if they just drink regular pop...
I don't have any ideas for getting a child used to the loving warmth of his mother to get used to the solitude of a crib, as my kids moved into their own beds on their own... quite a long time before I expected them to. Of course, I was far too lazy to go to the trouble of managing where they slept, preferring at all times to get the maximum amount of sleep possible for *me* whenever there was a choice to make. I couldn't sleep through my kids' crying, so I never made them cry without attending them (I was awake anyhow, so not going to them created more distress, and crying, for them and less sleep for me in the long run).
Unless you know why he's crying (if he's painfully hungry, 'knowing you are there' won't help, for instance), making him cry instead of attending to him will teach him things you may not want him to learn.