Jack burying Uncle and John and living with his mother at the ranch until she dies. Throw in livestock being russled, the ranch falling into disrepair and Jacks growing distaste of authority by having some scrapes with it

^ Some of that. Maybe Jack practicing with guns too.

Yeah, I feel like if we actually saw the transition for Jack from "awkward social issues having teenager" to "mentally composed enough to manipulate several government agents into exposing one of the most acclaimed Federal Agents of the time" and also generally being an unlikeable prick. I never get him that penny dreadful he asks for, or any other random stuff and I headcanon that to be the reason why he's such an asshole lol

The epilogue would feature multiple examples of Jack being kicked by horses which explains why he's a dick to them.