I'm guessing that coolant went everywhere including your distributor and belts. The clicking could just be the belts slipping, try spraying some carb cleaner on them with the engine running, if that eliminates the noise change the belts they were probably old anyway.
Your rough running might be ignition misfire from coolant in the cdistributor cap and on the wires. From what you've said about the car it probably needs a tune up anyway.
Passing a pressure test doesn't mean you don't have a blown headgasket, but overheating doesn't mean you do either. The M30 isn't as bad as the M20 or 50 in that regard so you could be okay.
If the cooling system begins to pressurize or it refuse to purge all the air then start looking for a failed gasket. Meantime check the above, the sky isn't necessarily falling.