Normally, if your just trying to pull and hold a vacuum on a short length of hose (with no large volume attached), you will not be able to hold a deep vacuum for a long time. Since the internal volume of the hose is so small, even the smallest of leaks will quickly raise the pressure.
OTOH, you say you could only pull to 400 microns while the pump is on. Usually, a decent pump with new oil should allow you to pull well less than 100 microns. So, it sounds like you have a rather large leak in your setup somewhere.
I would start by hooking the BluVac directly to your pump with the shortest hose possible (or a brass fitting) and no valves. See how deep your pump can pull (disconnect BluVac prior to turning off pump, or you might wind up needing to clean it!). Then start adding back hardware till you're back up to 400 microns. Then you'll know where the leak is.
At lot of guys here have also solved similar problems. I'm sure they can help you as well.