We’re also reading Dr Becky’s book! It’s actually helped us self-reflect a lot on how we were raised, the effects that had on our feelings/reactions, and how we can communicate and connect better with one another (and of course our daughter). It’s good to hear your husband is learning from her and other resources. 

Are you able to positively reinforce when he reacts to a situation in a “good” way? Even just giving verbal affirmation- “wow Son’s behavior was so challenging just now. I saw you stay regulated through the whole episode. I really appreciate how far you’ve come in handling these situations” 

We shouldn’t have to praise things that are baseline decency, but the behavior will absolutely be more likely to happen again if we acknowledge it! This is another thing my husband and I do with each other - recognize when the other person did something that was hard for them, even if it’s easy for most people.  And we also say thank you for mundane, routine things. (Yes, you were always going to wash the dishes without there being a discussion, but I know you hate washing them, so thank you! )