In my experience as a kid, directly managing my emotions was practically impossible at that age. That's got little to with autism though, a lot of kids are like that. The autism just means there will be different triggers than most other kids.
Many of my difficulties as a kid were in not understanding something everyone else just knew intuitively. For example, when playing a competitive game with friends, family, or classmates "The Game" doesn't actually matter. Which game, who wins, who looses; These aren't why people are there. But that's how everyone talks about it. Everyone pretends that's why they're there. The reality is they're simply using it as an excuse to spend time with each other. "The Game" serves no purpose beyond giving structure to a session of socializing. If you can explain that to him, and he can grok it. It'll cut off much of his concern for wining. Maybe not completely, as some people are just annoyingly competitive. It's possible he's one of those. In which case I'd recommend switching to cooperative games.
Changes in the schedule are only a little different. Again because of how most people talk about things, it seems they're fixed. When in reality most know intuitively, plans and schedules are dynamic. I eventually learned to do what I call "Planing for Chaos". I needed to learn that every schedule is only a hope, not a guarantee. And when inevitably things don't go as planned, I needed to come up with contingencies. Some generic: Put on headphones and listen to something while I wait. Others are more specific: If this doesn't happen, I'll go do this other thing instead, then check back. But it depends on understanding that the schedule is never anything other than a hope.
Disagreements are going to be the most difficult. I'm still not good at that. I generally avoid them, which I know isn't good. Mostly because when I don't, I will get... Intense. And I'm a rather large man now. It's extremely easy for me to intimidate or even scare people when I get upset. And that's never what I want to do. It generally works against me, no matter how compelling my argument.
Good luck. I hope that was some help.