You’ve already answered your own question, stop the progression once you’ve hit Coach Chad’s benchmarks. Or when you feel you’ve achieved the benefits you were looking for in terms of fatigue resistance on long rides. After that then continuing to get stronger is going to mean adding muscle mass that is increasing your weight without giving any cycling benefits, and is also impacting the time and freshness you have for cycle training. Ideally you’d want to stop the progression and move into maintenance before you hit the build phase on your cycling training, as I think it’s hard to do both at the same time.
The plan goes on forever because it’s aimed at people who want to carry on getting stronger/bigger, which isn’t cyclists. You’ll also find that you almost certainly progress a lot slower than laid out by the plan as you’ll be doing cycling as well so won’t be recovering and adapting to the strength training as rapidly as somebody who is only doing strength work.
In terms of what to do once you’ve hit your goals and are maintaining, I tend to mix it up quite a bit to keep from getting bored. Still hit the major muscle groups at least once per week. But I use more variety of exercises including doing bodyweight stuff that I can do at home (I don’t have your setup unfortunately!) or when travelling such as pushups, pullups, lunges, single leg bodyweight squats, squat jumps, etc. In the gym I might swap out bench press for flies, inclined press, declined press, shoulder press, etc. Would rarely do 5x5, more likely to do 3 x 5 or 3 x 10.