Family Gets Your Best or No One Gets the Rest Help?

[jandjmommy]

DS newly 8 has been yelling/disrespectful/hostile on and off for a few weeks. Some of it is likely a result of a very busy schedule (which he is not used to), including upwards of 5 baseball events each week. I'm wondering if he's upset because he isn't *with* the family even though we're present at all of his practices & games.
I don't know how to manage this and I feel like I'm doing it wrong from a GBD perspective.
Example:
Me: [after evening and morning review of our schedule for the day] It's time to start your math.
DS: yells about how he will not do it, I can't make him, I'm so mean, he hates math, etc.
Me: It's time to start your math. You want to go outside right now and you'll have plenty of time for that after math so let's get going on it.
DS: yells again, or says he's sleepy and throws himself onto his bed.
Me: Fine, you're welcome to take a nap or rest. When you get up we'll work on your math.
DS: yells again, escalating negativity.
Me: We have a lot to do today. [baseball] Practice is at 5. We have to leave here at 11 to x, y, and z. I have time now to help you with math, or I have time at 5. You need to call your coach if you choose 5.
DS: yells and starts his math; simmers down after about 20 min and is happy with his progress when he's done.

So that's when he's just yelling. Is that OK? Several times though he's been very disrespectful towards me, not just angry and voicing his opinion of doing [math]. Then it goes like this:

Me: You are being disrespectful. It's ok that you don't feel like doing math but it's not ok to speak to me like that.
DS: sometimes calms down and apologizes, and we're good; sometimes escalates.
Me: You need to stop being disrespectful. If you do not recover you will not go to practice since I can't trust that you won't disrespect/be negative with the coach or your team.
DS: sometimes recovers and we talk about ways to do that; sometimes escalates.
Me: You will not go to practice today. Do you want to call Coach or do you want me to? I texted the coach. You need to apologize to him for missing practice tomorrow at the game.

He missed one Cub Scouts meeting and one baseball practice this way. Then warming up before a game he started being rude to DH and me, and saying negative things to his teammates who were warming up with him. I took him aside as casually as I could to help him save face and told him that I would take him home if he did not recover. He continued, so I told him to go tell his coach that he had to leave. DH then stepped in and gave him another chance, and he recovered well with no further problems.

I don't want to punish him but I do want to require that he respects us and his team/friends/etc. How to follow "family gets your best or no one gets the rest" the right way -- or is that really GBD? Should I just try again and again and again until he recovers or is there a point at which he truly should not put in a situation outside the family where he may negatively affect others?
ETA: DH and I disagree on having him miss activities. DH says he has a responsibility to his team. I say he has a greater responsibility to his family. --?