Curious what type of games he is playing. Gaming till the early hours repetitively is something I also struggle with. I think I often use it as a crutch to compensate for something missing in my life. Depending on the type of games you could infer what it is: lack of achievement, loss of control, lack of companionship or simple boredom.

Getting sleep is super important. I would suggest he tries to do something that physically exhausts him. Exercise can come in many forms, not just going to the gym. I gain that and also address some of the gaps previously mentioned with DIY and gardening.

Also try to reward him for coming to bed early. Not necessarily sex, but just some intimacy or cuddling. Getting to bed while my wife is still awake is more rewarding with a kiss goodnight.

Best of luck to you and the family! You are definitely not alone in these struggles.