Not to wade too deep into the “is Chris really trans “ debate, but I remembered the ‘boys should play with transformers to reaffirm their masculinity’ video. I’m not the closest observer, but has Chris touched or mentioned transformers at all since the start of the tomgirl saga? Similarly, was he into mlp or anything similarly feminine before then?
If those are the case, it’s insanely funny because Chris’s gender expression is so closely tied to consooming. To Chris, a critical part of being a man or a woman is just the toys and media they consume. It’s an incredible understatement given all Chris has done but there’s a lot going on there.
To really stretch the extrapolation, I wonder if the incest would have happened if he still saw himself as a man. He’s always had warped gender views and it makes me think Chris may view sex as almost unrelated concepts depending on a person’s gender.
Somebody once said that Chris has always had a deep-seated hatred of his own gender, as well as what society expects out of him being male.
That talk about 'boys should play with Transformers to reaffirm their masculinity' reads to me as something that he was taught that he's merely regurgitating.
Back then, Chris's morality centered around what he was taught and told by his parents, hence his abhorrent views on people of colour and homosexuals.
This is why he took great offense back then to being called 'gay', because his church and his household told him that it was wrong, and not because he genuinely believed it.
And to answer your question, Chris was into girly things for quite a while now. My Little Pony was in his life long before bronies was even a thing, but even before that, he was into things like Sailor Moon (then again, he could have just shown interest because of Megan and because it was fap material for people of his mentality as well.)
As for whether he would have fucked Barb if he never trooned out? Definitely. People were sensing it long before he decided to become a Tomgirl, hence why there were pictures drawn of Chris fucking Barb to mock him. Here's a fun fact: In some nuclear families, when a parent dies, the surviving parent may fall back on their children to provide some form of 'emotional' support to fill the void. And, unfortunately (in rare circumstances, mind you), sometimes this fall back does involve something sexual. Barb raising (see: emotionally abusing) Chris involved things like spooning him, and forcing him to sleep close to her, on pain of her threatening to kill herself or trashing his room if he doesn't comply. To his credit, Chris outright resisted this at first, but there's only so much that you can do when you're under the thumb of an abusive parent, especially when the alternative was to move out (which Chris couldn't do, given his crushing debt and poor impulse control when it comes to spending.)
Point is: Chris being trans had nothing to do with all of that. Barb would have still manipulated him into that twisted way of thinking, Chris would have concluded that Barb was the only woman who'll ever be that close to him willingly, and might as well go for the gold since Bob's no longer in his way and, despite what he'd tell you, Magi-Chan and Mewtwo are fictional and won't suck him off for real.
It's also highly likely that Bella came to this realization a lot sooner than we thought, and put plans into motion to capitalize on that sexual frustration. Again, Chris being trans would not have stopped him from encountering Bella and her deranged behaviour. He would have been manipulated just as easily if he was still male.