I totally agree with you. And the emotions he showed through his words, body language, and facial expressions in that latest chapter were just too raw and genuine. One of the best father/parent redemption I've read, so far.
Yeah. His bad parenting is not wholly his fault either since he was kept in the dark: 1) the servants and his kids basically told him Penny was a problematic child and lies to him 2) OG Penny often showed only her worst when he was around bc the harassing was too much + OG Penny never called him "father" so he thought he was hate by her and kept his distance and relies on others' rumors. 3) all the nobles lies about OG Penny being a wild problematic girl.
I think his fault are 1) trusting TOO MUCH the mansion staff bc he knew they looked after his kids well and was naive to believe they would do so for the stepdaugther too. Plus the staff follows the example of his sons that mistreated Penny 2) never tried to talk it out with Penelope, he just gave her jewels and food thinking it's all fine and stay in his study. 3) trust his sons more than Penelope which is not favoritism considering the lies they told him is backed up by the staff that hates Penny.
His situation is very much a "if you're only told lies without knowing they are lies, you think it's true."
... unfortunately he doesn't realized that Yvonne's returns is very risky for Penny's life. It hurts seeing him getting rejected by Penny but yeah she needs to survive. He really does care and wish to give Penny the love she deserve.
I know others hate him bc "It's too late" but I hope they realize the dad/duke DOESN'T WANT to be forgiven by Penelope but just want to atone for the bad parenting he has done. He's being a proper parent that looks after his kid because she is his daughter, period. And he's NOT DOING so because he wants something in return (Penny's forgiveness and love). Yeah, he did a really bad job as a parent but he's redemption was really nice