You'll get a direct answer to Battler's linage in episode 9. I really recommend you get to episode 8 ASAP. Ange is more important than any of this. You'll learn why. I also think it will change your perspective a bit on the blame game. Its a bit of distraction IMO. Also, there is some other stuff that's not in the visual novel, but was only in the manga. There's controversy if its canon, but its called "The Last Note Of The Golden Witch." Someone made a visual novel adaption of it too on Y.T. It should be the last thing you read. There's a bit of a meta-discussion on the nature of Umineko here.
Also, on your other point. There were multiple Beatrices. The first one he fell in love with because he was a suicidal young man running from his tyrannical family into WW2 hoping to die, and had a child with her that he also named Beatrice. He didn't care about the gold, status or the money (he ran away from that). He genuinely loved Beatrice - too much actually. Beatrice's coincidental appearance in his life gave him a reason to live.
Kinzo did incest with the child of the first Beatrice (Second Beatrice the hostage) to make Yasu (Third Beatrice). Kinzo is more or less just a very naive man who grieved his widowed wife to the point of an unhealthy obsession because she died so young. Again, this was the woman he owed his life to.
His actions aren't defensible, but he is a tragic character who's a bit of a product of his circumstances and time. Genji, Nanjo and Kawa were pretty nice to Yasu, and were just trying to make the best of a shitty situation since you can't really oppose your employer. Especially one connected to a powerful Zaibatsu family. Natsuhi was really heartless though. You just don't do that to a baby. But, women don't really have any say in Ushiromiya matters, and that did influence her decisions as it did Rosa and Eva. I think the one thing you should take from Umineko is how strongly feminist it is and that's not really a coindence since this was also the case in Higurashi considering Takano's back story.
Yasu was mentally 'ill (ofc who wouldn't be after what happened to 'em?), and the murderers are largely because Battler forgot his promise - which Yasu took too seriously even though he's a sardonic guy. And he didn't know anything about Yasu. A simple mistake leading to a butterfly effect all because he was just trying to be friends with a very lonely, abused person while being totally oblivious to no fault of his own. I think this should have been covered in EP7/ insinuated in EP4 but forgive me - I haven't read Umineko in years. I think I may have forgotten some stuff. There was a similar theme like this in Tsukihime and Higurashi if you're familiar with those works. But really, the whole situation is really just an avoidable, unnecessary tragedy. Its just sad
Okonogi is one of the more interesting characters, and I really think he flew under the radar, but had a lot to do with what happened from the other world perspective. However, this only becomes clear if you know anything about Higurashi. I haven't touched Cicionia (the sequel to Umineko) because its not finished yet, but I know he plays a role in it. You shoild recall his conversation with Ange in EP4. Its a very important piece of information that can change how you look at stuff in the entire novel itself.
"Without love, it can not be seen."
