Yep, you've got him figured right. Separating him will definitely let them get settled with the other hens easier, I just hope he doesn't stress out too much. The last pullets I added were about that age, but he still chased them off and caused them to be pretty skittish even with the other hens once they had gotten used to the pullets.
I actually went for the introduction today, but with a different approach. I don't trust the new ones yet to free range, so I added one hen at a time to the large run. Starting with the nicest, and adding the top hens last. It went very well, and the pullets remained calm. At dusk, I ushered all of the hens in the coop ( a dog kennel coop ) including the pullets. They roosted on a separate roost, but I think it went well. I know there will still be some pecking, but it was much easier without the roo ( who had already been separated into a small coop)