Happy Holidays to you too Zach!
Catching up on things after my travels, and the holidays. Still dealing with trying to find which box I put that thing I didn't think I'd need, but ended up needing right away 🙄
Anyway, to your questions:
As far as practicing in the backyard compared to how much you play. I think you'll want to do a fairly good chunk of more variable practice, with a preshot routine, to simulate the on-course challenges. My two favorites are either the 4-club circuit or playing your course on the range. In both of those scenarios, you don't get to hit the same club twice, so it makes it harder to "time your bad swing" and forces you to come up with a recipe for each shot.
What do you do with your hands? Attached are 2 sets of graphs (trail and two lead) for two players. The follow-through part you're talking about is the right half of the graph past impact. I put a yellow square to indicate that space in one of the graphs. Flat horizontal lines mean that nothing is changing. So you'll see that for most of the graphs and lines, there's very little change in the hands/forearms during that zone. To do little with the hands, you have to do more with the body. Specifically, the blend of extension (probably most important), side bend, and rotation of the spine.
Low left exit thoughts are usually bad for golfers who get over the top at the bottom with the shoulder blades.
You can rotate the club with the forearms, or the shoulders, so that shoulder move you like can cause the club to rotate, even if the forearms are stiff and doing very little. In this follow-through screenshot, you can see that your thoracic spine is still flexed, and the right arm has a fair amount of protraction, that combination usually aligns with a dominant shoulder move at the bottom. It lacks what I call bracing and can easily contribute to hooks.
I think it's good to know which arm you are more dominant with, but you might benefit from some trail arm focus in practice. You can always think about the lead arm when you play, but training less throw of the right arm might help the lead side behave.
The little hop move is influenced by the rib cage being back a bit (not covering the lead side) which is really common when the shoulder throws at the bottom.
The setup epiphany makes sense. 👍
Eating the deltoid comes from the lead shoulder shrug, that's a good shallowing move to do later in the downswing. Also, if you look at his backswing, he tends to stay flexed in his spine a little more than most in the backswing, so that deltoid much is a way to create arm height if the spine isn't doing it.
Here's to a good 2024!
Happy Golfing,
Tyler