It could be that you are running to lean on the bottom end and once your idling the fuel is vaporizing??? I put a question mark there because it seems odd to have any kind of bubbling or to be able to hear noise when the engine is running. When you run an engine too lean it becomes hard to start when its hot. I would say richen up both needles at least a quarter turn if not more and get it warmed up and tune it from scratch.

As far as the moisture in the pressure line, that is normal and its unburnt fuel/oil being pushed back to the tank. That line is what pushes the fuel from the tank to the carb when the engine is running by exhaust pressure.

As for your main bearing, you would only need to replace the front where the leak is. The rear isnt a cause of that. The problem is when you run overly rich for too long, like when you break the engine in, the fuel/oil pushes its way through the bearing. Also, when you shut the engine down you should burn off everything thats in the tank and lines running it out of fuel and trying to restart it a few times to burn off as much as you can thats left over in the engine.