S.,
My son was 15 months when my third baby was born. I too took the binky from my son before the baby's arrival so I wouldn't have to worry about him taking it from the baby. Hind sight, I absolutely would have done the same thing again. It has been well over a year since he has had a binky and on occation he still snaches his little brother's binky.
If I were you, I would try to get him into his own room ASAP, especially if the baby is going to be taking his place in your room. You want to do it well enough ahead of the baby's arrival so that he doesn't have resentment toward the baby for taking his sleeping spot. My boys (the two youngest) share a room and I made sure that my middle son was out of the crib and in a big boy bed months before the baby's arrival. They are already going to have enough adjustment, and yes some resentment toward the baby without adding to it by making them feel that the baby is taking everything that is theirs. How to do it? The only thing you can do is just do it! You have enough time right now that you could start him out in there for part of the night and extend the amount of time daily. He may surprise you and take right to it. I built up the big boy bed so much that to my surprise, my son took right to it. It may help to postition his bed in the same spot in his room that its in in your room.
I would bet that your son is acting out because he is really starting to sense that a major change to his life and routines is coming his way. At five months along, I bet your body has just now started to change in ways perceptible to him. Reassurance, patience, and love does wonders. It is hard for little ones to go from being the center of your world to sharing the spot light with a new baby!
It is all worth it though. I am amazed daily by the relationship that my sons have!!
Good Luck and Congrats!!