You might try dividing the coop with a piece of wire fencing, so the pullets can have one side and the cockerel can have the other side. That way they can get to know each other without the pullets being in any danger from the bigger, more mature cockerel. And he won't be completely alone, since being alone isn't good for any chicken.
You can let them be together if you supervise them, so you can grab him if he causes a problem. But having them separated when you're not there will probably be safer, at least until you see how they will act.
Chickens are individuals. I've read of cockerels or roosters that seemed to adopt chicks and care for them, and I've read of some that tried to mate pullets who were too young and the pullets got hurt. And of course some would ignore the chicks, and some others would just generally pick on the chicks.
Once you've watched him with the pullets, you will have a much better idea of how he will act with them. Things can change from one day to another, but in general his own behavior will usually be the best predictor of what he'll do in future.
Sorry, I don't know about the crowing.