How much of Chris's faults are his direct responsibility? It's easy for us to look at him and say "he should have learned" and/or "he knows what he's doing" but can we be sure of that? I think not.
I'd say there's three pieces in that puzzle you're not accounting for.
1: Chris deliberately concealed his actions from the majority of people, including Null. That suggests he knew it was wrong.
2: He alluded to having a relationship with an older woman to Null. So he wanted to brag about it, but still knew it was wrong, while still wanting to brag.
3: He's not as psychotic as people assume. When he was suddenly rendered homeless, he didn't walk around the streets of Ruckersville trying to use his CPU Goddess Powers to manifest resources or ride the energy produced from the dimensional merge to alter reality. No, he got in his van and then used his phone to funnel money out of Barb's account, and then tried to lie about it.
Chris is a severely autistic man who was stunted by Barb. But while he likes his make believe, he's neither unaware of what's right and wrong nor is he entirely removed from reality. He has shown some incredibly low levels of cunning and manipulative behaviour and while he's generally a bit of a coward, he's either a danger to others who are weaker than him or far too easily lead into being a danger to others.
Remember when he tried to run over Snyder? It's speculated that Barb was egging him on, but either way he tried to kill Snyder with his car. Upon getting off lightly, he proceeded to smear Snyder by claiming Snyder had staged the entire accident, Snyder was a child molester, uploaded candid photos of Snyder all over the internet and even made a voodoo doll to torture him (again, his autistic make believe coming to the fore).
Is Chris a danger to the general public? No. But if Chris develops a seething hatred of someone else who tells him no, or finds another vulnerable disabled woman to make into a surrogate Barb, something bad could happen. It's not Chris's fault he ended up the way he did but he's still capable of being held culpable for his actions.