I say kudos for getting rid of the pacifier! If you are co-sleeping, try nursing him laying down and then pulling away. That is an easier fix. The best thing to do is work toward nursing him until he is ALMOST asleep and then letting him finish falling asleep on his own. I HIGHLY suggest reading The No Cry Sleep Solution by Elizabeth Pantley for suggestions on how to do that gently - for you AND him.
You are away from him during the day and he simply NEEDS you at night. That is HIS time with you. There is nothing wrong with nursing for comfort at his age. Plus, this will keep up your milk supply so you can nurse him as long as possible. VERY important for a working mom. I would encourage you to view this time of nursing as very valuable to your son's health and your relationship with him. Bring a book while you nurse or even pray or meditate. As a single mom, it's especially important for you!