I agree with all of this except the sit-ups part. I used to do tons of sit ups and crunches but found this only exacerbated hunched over posture. I think you would agree your body needs as much muscle around your lower back as possible to keep it in alignment and handle the stresses of grappling, particularly an aggressive top game (like mine) where you're regularly attempting passes, takedowns and initiating scrambles.
Three best exercises I've found to achieve this are in order: deadlifts, squats and hyperextensions on a roman chair. After I got my power rack for the basement, I only do the first two and they've kept my back strong and healthy for grappling.
You also touched on and can't overemphasize the recovery aspect. I'm a believer that there's no such thing as overtraining. Only under-recovery. As an older guy now, I can still go balls out in training and redline myself to roll 6+ rounds full speed, back to back. But if I do that I need to take at least the next day off with good sleep and preferably 2 days. No way I can do that every day, sometimes twice/day like I did in my early 20's. My goal now is to rarely if ever redline my body, so I avoid training when I'm feeling run down. Since I started doing this, my injury rate has gone down dramatically.
