It's easier for you to beat up on yourself like this when you're feeling crappy....who wouldn't with all that going on plus impending surgery?
Yrs ago another member here suggested adding an "S" to HALT to include "Sick" in the acronym - that always made sense to me. It's easy to spiral in negativity when I feel like walking garbage - like attracts like, right?
So let's revisit the hard work you've been doing & the breakthroughs you're seeing with DS in just the last couple of months since you've steeled yourself for the coming battles:
Originally Posted by
CentralOhioDad 
I have been 'priming the pump' with conversations about: people argue, people have disagreements, it's a brand new year and with each year comes change - some changes make us happy, and sometimes changes make us very sad - but in the end know that mommy and daddy love you more than anything, and the daddy has only what is in DS's best interests, though it may not always feel that way. But, he needs to know that I love him and he needs to trust me. And one more thing - he is not responsible for anyone's feelings or happiness, that needs to come from within.
Originally Posted by
CentralOhioDad I've been 'talking, talking, talking' (per FireSprite) to DS7 about being truthful to each other, talking about feelings, accepting change, knowing that I love him more than anything, that he needs to trust that anything I do/say/decide for him has ONLY his best interest in mind. I've told him that life changes all the time, and some is good, some is scary, and some just downright sucks - but that I have his back, always.
Obviously it doesn't mean much to him now, but I continue to reinforce it so that once things start falling apart, hopefully he understands that it will be okay, at some point in time, and I will NEVER ever abandon him.
We were taking dog for a walk last night and he said, "You know what, Dad? I know in the past that I had a hard time listening to you when you were trying to teach me baseball. But I realize now that you are right and that you only tell me things to help me. I don't always like it, but I'm starting to understand that you are just trying to help make me better!"
That was so awesome! I went on to tell him that how I guide him and teach him is more than just baseball, that anything I do is for his betterment.
You are BOTH growing tremendously already and you've only just begun to really bond over/through all of this. You can continue leading him in dropping Codie behavior as you yourself get the time & space to do the same - my biggest motivator has always been seeing ugly symptoms surface in DD, recognizing if/how it's a mirror of my own behavior & addressing it there first. I'm essentially reparenting myself alongside her as she grows up. (I'm not saying I like it, or that it's easy at all - lord no -but it does bring me some of my greatest real-life growth moments.)
When we know better, we do better - that's what you're doing... and you're already getting feedback from DS that it's getting through - he
gets it. 
(and since I'm shameless - I'm going to plug Brene Brown's work AGAIN - The Gifts of Imperfect Parenting is a short book/audio CD & IMO it should be a staple for every Codie Parent's reading list. I cannot recommend it highly enough.)