Tell that to professional sports bettors and poker players
Magic words. Professional bettors. I wonder how many of freebitco.in's player base call themselves pro's. You can't be a pro if you don't make a living out of it.
But hey, you can keep sticking to your free rolls if you want.
I don't think it is +EV when you lose. (In your example, Arsenal won, it wasn't a draw)
Your calculations don't take the probability of landing on a fixed result match neither. (yeah sometimes people cheat)
All I am saying is, you can increase your chances by doing fancy calculations, to an extent but in the end it is still about your luck. +EV is not guaranteed.
Clicking the button however, is %100 +EV, that's why it pays so little.