Chris can't cook or clean and views pulling weeds as something akin to the construction of the Thai-Burma Railway, so for looking after most people, I would say definitely no. But Barb is fine with living in squalor and eating crap, and Chris is perfectly capable of providing that.
I think, though, with her advancing years, Barb is getting harder to deal with. Hence Chris' desperate attempts to reconnect with other family members. Barb is already crazy and paranoid, and senility would probably make her intolerable. Chris can't cope with people acting like normal human beings, God only knows what he'd do if Barb woke up one morning thinking it was 1963 or something. Due to his lack of theory of mind, his response when people aren't doing what he wants is frustration and anger. And lest we forget, he's incredibly selfish. If she started wetting herself, say, I could definitely see him ignoring it. Probably justifying it by claiming that she's trolling him.
Then there's his limitless capacity for stupidity. Really wouldn't put it past him to think, "Well, if I gave her All Her Meds now, then I would Not Have To Worry About It for the next month, which I plan to spend Tribbing Hot Lesbians."