My head hurts

So I've spent several hours reading assorted wells of 40k lore. I have always known about the Alpha Legion and the whole Alpharius/Omegon shtick, I never really delved too deep into it just accepted it as sort of a meme. However now I have delved deep into it. Nothing makes sense. Alpharius joins Horus even though he is shown by the Cabal it will end humanity? If he is a double agent he did an absolutely horrible job at it being the master of sneaks. Omegon apparently also betrayed big E but then he is loyal somehow? And he tried to destroy Alpharius? But then whichever one of them saves Corax? I'm guessing it was Omegon, but then nothing is said about it much later. The Emperor doesn't know Omegon exists for some reason, either that or Alpharius killed Omegon early in the Heresy. Alpharius basically lets Dorn kill him? Why? Don't tell me its a fake Alpharius because if a primarch cant discern his brothers to an Astartes then nothing works no more. No one knows where Omegon is. Why? What kind of scheming is he doing that is bigger than helping the Empire? Is it supposed to be this stupidly confusing and did I just take the writers bait or am I missing something stupidly obvious? I am frustrated because I like the idea of them two, but I have a feeling the writers didn't know what to do with them and just made them more and more confusing to the point that its a lost cause anymore. Can anyone help enlighten me please?