I'm pulling 90/10 out of my ass, but the point is that your weight overwhelmingly depends on what you eat rather than how much you move. You can't out-train a bad diet.
All of the stuff you mentioned below is fine advice for someone who's already a normal weight (or only a bit overweight) and wants to increase their health, but look at Boombl4: he's extremely obese. If he tries exercising properly now, the benefits he will reap will not outweigh the strain he'll put on his heart and his joints.
And at the end of the day, losing weight is just calories in vs calories out, so I would advise him to simply lower his calorie intake and cut down on fast carbohydrates and trans fats until he reaches a lower weight, at which point he could start an exercise plan. Not to mention the fact that it requires much less willpower to simply eat healthier food than it does to stick to an initial exercise plan, and that is a big deal for fat people who need to learn how to discipline themselves better.
But ofc I am not a nutritionist, so I'm not saying I am right and you're wrong or anything, this is just my opinion about what would be best for him.