I would implore you to try and make amends with the mother or at least be on a neutral level before he gets into HS, I've gone through this scenario myself, maybe not as a Hapa but as a son with separated parents. It's okay to talk to him about what she says when you're not around, but try not to put your own negative connotations on the marriage or the mother. If she's always flinging mud and you're not then he'll see the unnatural balance of things. If you sling mud as well he'll feel like he needs to be the moderator. Try to get it to a point where he calms her or tells her to talk to you when she brings up stupid shit that he shouldn't have to be worrying about. That's the best case scenario. Then with you and her at a neutral footing you can try talking it out calmly without escalation. You don't want your boy to be me. Take it from me, you want him to be better, you sound like you've got a good head on your shoulders and he'll be fine. I wish you the best of luck.I always wanted to be with my dad too because he had less custody. Having to be the full custody guardian and the full time disciplinarian changes the dichotomy but not by much. As long as you discipline at the same level he's used to.Hope none of this comes off as all knowing, or telling you how to do your job as a father. I just want to save future kids from having to deal with what I did.