it will be  a dropwise lubrication, the needle valve shown in scheam is for the same purpose i.e to adjust dropwise flow for lubrication, and flow indicator provided, so that operator can visualize that dropwise lubrication.
Tentatively that flow will be around 0.5 to 0.6 LPH,
any lubrication oil you can use for bottom bearing  lubrication, only it should have lubrication property, good flowability at ambient temp.
for oil flooded mechnical seal at top oil recommendation  is SAE-40/equivalent (which already mention in GA drawing)