
All this stuff about exposure factors and equations is naff ... it's putting you in at the very deep end and it's very unnecessary. Use your exposure meter to read the scene, extrapolate the result to the pinhole and shoot and forget about fancy fractions and mathematical gymnastics.
I'm learning of many people getting too involved with the mathematical side of pinholes, including something called Raleigh's Theorem (?). It's absolutely not necessary (it may well be when designing a pinhole).
An EV is a logarithmic expression of the constant quantity of light equal to a set shutter speed and aperature value. Think of it that with each change of the Av/Tv quantity of light is doubled (or halved).