The MOI is not something you calculate but something you adjust to. You should know the number of cells you are adding and the titer of your phage stock, so you select the MOI you want to have and adjust the volumes of phage added to the known number of cells to reach that MOI.
For EOP that is a relative value to some known mechanism of counting your phage. So you may have a good host and you know your phage titer is 1e8 for example. And then you plate on a different host and you get a titer of 2e7. So the EOP would be 0.2 or 20%. But it is calculated relative to some known control value.