I have been running/building dry sumped setups since 1972---I have never seen or heard of a tank draining into the engine to find its own level---if it were to do that--it would have to pass thru the
oil pump( highly unlikely) pass thru the lines to filters/coolers ( again unlikely with only a few inches of head pressure) and then have to go thru the engines
oil galleys/bearings,Etc.
If the system is blowing
oil out the top of the tank, the breather/separater system/method is inadequet
With a current tech dry sump pump a vacume pump is unnessary as it is possible to pull over 20 Hg with the lobe type scavage pumps and 10-12 hg with the old tech gear pump
Jerry