1. The exit connects directly to Coolock Lane. The name is carried over from the older road  that got split in the late 1980s to construct the N1. The two remnant roads are not signed, but still called Coolock Lane by locals.. confusing yes
2. The exit is indeed J2. J1 is down in the port, and J3 is at Ballymun. Perhaps you are confused as most people don't know that this is the M50