i would close the hole with some fitting, use some pfte tape around it too, to seal it properly, as for a static you dont really need an outlet at the bottom to gravity feed anywhere, though my ibc is 100ltr with a tap at the bottom, and i use this petrol pump but sub pumps are good.
You can get a decent petrol water pump from Aldi's £100 that will pump 650ltr per minute... with a hose through the lid and delivery hose so your van tank will be full in 45 seconds ish..
though sub pumps are quite good.