on bro being abusive: i don't believe its been completely confirmed or valididated on how he used dave for his pornos. most people believe that he wasn't directly involved, but we may never know exactly what he did
On page 2470, Dave says he “may have just been an unwitting accessory to some sort of grisly puppet snuff film.”
And then said he wasn’t sure how he felt about it implying that it wasn’t something that happened often, but Bro also had hidden cameras all over their apartment so Dave may have unknowingly been apart of them before. But like you said, we’ll never know exactly how he was involved in them.