I'd do a compression and leakdown test before throwing any more parts at it aside from the plugs. A flashing CEL misfire can be indicative of a burnt valve among other things. The CEL may be causing the car to go into limp mode.
You can try moving the coil pack from cylinder 2 to another location. If the misfire follows to the new location then you know the coil pack is the issue.
My 03 WRX had the flashing CEL and it was caused by a burnt valve.