He compares their marriage to his relationships with them, for sure. I’m not sure how far he goes in comparing Belle herself, other than on the level of pathetic gratitude that she’s so tolerant compared to Milah, and so gentle and generous compared to Cora. That she’s willing to put up with him, basically. He’s far, far more aware of his own behaviour with them vs his behaviour around Belle.
I don’t think Rumple is capable of letting go of love, so I think he still has that for them, but he must’ve had a lot of hate to murder Milah, and I think he was genuinely horrified by Cora’s decision to tear out her own heart. Anger is poison to him, but he tries to use it as armour. As his trust in Belle eats away at that, all his conflicted feelings about a lot of his past must be eating at him. He recognised Belle’s unhappiness in the chapter before last in terms of Milah’s frustration with him, all those years ago - and knew he had to do better, with this new wife. I suspect he was comparing her to Cora, or at least reliving that anger and revulsion, when he thought Belle had betrayed him.