WHY DOES OIL BLOW OUT DIPSTICK TUBE WHEN ITS RUNNING

Depends on the cause.
Blow-by is when oil blows by the rings in the cylinders into the combustion chambers or compression blows by the rings into the crankcase. It can also be caused when too much pressure builds up in the crankcase because of a venting problem.
So blow-by can cause smoke out the tailpipe from oil burning with gasoline, or oil collecting in the air cleaner, or blowing out a seal or other place like your dipstick tube.
If it is caused by worn piston rings, the rings have to be replaced.
If it is a venting problem, you need to open up the vent, like the PCV valve or the air intake port.
If you remove the cap where you add oil and there is a vacuum when the engine is running, the venting system is working. If oil blows out the hole, there is too much pressure in the crankcase.

I would look for other leaks. If you are sure it's leaking at the dipstick tube, there is normally an o-ring where the tube presses into the engine. In general, this is an odd place for a leak, as ther eshould be no oil pressure in the pan (where the tube terminates) and unless the engine is overfilled with oil, the tube end shouldn't be immersed in oil to leak. IF there is pressure in the oil pan, that generally indicates bad rings. I have seen engines where the oil dipstick actually pops out of the tube under pressure when the engine is running due to pressure in the oil pan from blow-by at the rings.

Two possibilities I can think of.. Dipstick not fully inserted... or is it possible that you have overfilled the crankcase with oil??? On my VW, I learned the hard way to take special care when checking the oil level with the dipstick... I had to fully remove the dipstick... clean it off... and THEN reinsert it... and pull it back out.. and then look to get an accurate oil level reading... It must have something to do with how the dipstick tube runs down into the crankcase....

Excessive compression loss past worn piston rings into the crankcase .

No solution from me, Note: Sounds like your pretty familiar with the Positive crankcase ventilation (PCV). You said the valve is pulling a vacuum I am assuming it is from the intake manifold side correct? With the PCV was working sure seems like it would keep the oil from coming out of the dipstick tube. I am stumped as well, sounds almost like too much blow by from the cyclinders you already stated that with the possible broken compression rings?

The PCV system is supposed to pull vac on the crankcase to re-burn the fumes in the oil pan.
But your engine sounds like it has a vent problem via the air filter.

Your PCV valve is usually about a $2 part and is suppose to keep oil out of this tube. Follow the tube back to the valve cover and the PCV valve should be there.

Excessive blow by could also cause oil to get into this tube. The blow by is usually caused by worn piston rings or valve guides. The compressed air/fuel mixture or exhaust pushes past these areas and make it into the crank case. Usually if you have a lot of blow by, you'll see your dipstick tube popped out a bit too.

PCV valve is cheap and easy to change... I'd give it a try.

wipe the dipstick off well,check 2 or 3 times if there is compression problems it might blow some residue oil back up dipstick tube, [and dipstick out a little bit][rings] sure fire test, drain oil,change filter fill with new oil if you do not no proper amount try 4.5 litres and go from there.

On top of the valve cover there is a fresh air breather unit. Make sure the breather unit is not plugged.
Also the fixed orifice PCV should be clear. Find a tool that will go through the orifice and make sure it is clean.
Remove the vacuum hose and check it for cracks or internal damage. With the engine running, make sure you have vacuum through the hose.
Let me know when your finished cleaning the crankcase breather system.
Regards,