I think you need to look back to the start here.
You set it to 50 psi, then you checked it and it was 30 psi, so you increased it to 50 psi, then you checked it and it was 75 psi.
It seems to me that the malpassi didn't change it's pressure at all. Either you stuffed up the reading of the pressure when you thought it was 30 psi or your gauge read it wrong.
It looks like you got an incorrect reading, increased the pressure, got a correct reading, reduced the pressure back to where it should have been.
That said I also am not a Malpassi fan. I had one and had erratic fuel pressure so I ditched it.