“He had not forgiven Anne Elliot. She had used him ill, deserted and disappointed him; and worse, she had shewn a feebleness of character in doing so, which his own decided, confident temper could not endure. She had given him up to oblige others. It had been the effect of over-persuasion. It had been weakness and timidity.”

I think that you are right that CW notices how Anne is treated but I believe he chooses to consider it as exactly what he might expect for someone who gave him up and let herself be persuaded from him—her situation bolsters his own ill-used feelings and manner towards Anne. I agree with Jenny Allan that it is an act of kindness by CW to help Anne with the child, perhaps he is beginning to see the truth about Anne through his anger.