I like you're theory about Priscilla wanting the child.
But do you think perhaps that they both wanted it? Maybe he did know that the illegitimate child (I think so too), and he wanted to prove to his wife that he is in it this time it's for their marriage as said in an older vlog during Vlogmas? She already trapped him with Isaiah, and that didn't work out and he wanted out of his marriage, and that's when he had the extramarital affair.
I like where you went with Priscilla holding a grudge towards Assa because Abbie is the way she is, even though it's not Abbie's fault. But that doesn't explain why she clocks out of her parental obligations and feelings towards her daughter. There's no maternal bond, and it's not because she doesn't feel maternal (she is maternal towards her son and was raising him on her own when Assa left) she chooses not to be maternal. And it's obviously only for the cameras. Maybe instead of having a grudge towards Assa, she actually has a grudge towards Abbie or it's both? It's hard to tell with these vlogs.
What they say about Abbie being truthful, I believe because it's pretty clear that she doesn't even want anything to do with her too, because she wasn't there for her unlike Assa. You see plenty of times on the vlog where the mom is asking for a hug Abbie refuses, but most of the time if her dad asks for a hug she's there in a second (unlike lately). This is why when you see them on camera hugging Abbie it's always the mom bear hugging Abbie or she is forcefully kissed by mom because she obviously doesn't want any thing to do with her.
It is a sin to have sex with someone to whom you're not married to Biblically. So is that obviously both of them are not religious. And if they are Catholics, they are probably just going to Mass for Christmas Eve or Day like a lot of Catholic people do. Isaiah was conceived out of wedlock (they were not married before he was conceived). So essentially that is a sin, and people saying that marrying someone before they give birth corrects them of the sin. I don't know if theologicaly if that's true or not, but that is what seems to happen. Not just them, but a lot of Catholic people do this too.
Lastly, I don't think Assa is a good guy at all, he just sits there smiling at the camera spitting out verbal garbage daily, but inside he's a miserable SOB and hates his life. Priscilla clings to him for some reason, has no opinions or thoughts of her own. Appears to be a little stupid or a little slow herself. She's just a shell of a person. Now look at Isaiah with his crappy parenting upbringing that he received he became a narcissistic egotistical brat and momma's boy. His weekly vlogs make me not like him anymore. Yeah they're definitely bad parents. Don't even ask my opinion about Abbie, I feel bad for her daily. All the information and skills she actually learns at school or at ABA therapy gets thrown out by the bad parenting. She only vacuums on camera, she only does laundry on camera, washes a dish on camera. If the camera is not rolling she doesn't, and I have no doubt in my mind that she's rocking on that couch doing nothing maybe listening to music or watching tv but that's it. If she was mine, I would feel devastated, but I would find something she likes to do and do it with her.
. Maybe just gaining weight and hiding it.
really loves herself , this 
