Not a parent, but parents D'ed when I was 10. Parents fought bitterly over me and several issues that involved me. When I grew older I realized the why's and what's of a lot of court battles. Saw my dad go to jail cuz he wanted me to go fishing on a monday (no school) morning. Also saw the interior of mom's car pretty well ruined because dad made me commute with my dog when I was at moms. Just a couple of examples of what not to do.
You both decided to bring child(ren) into this world, and you both need to work together to raise a well adjusted child. There are a lot of pitfalls for kids to get lost into (drugs, gangs, bad grades, lots of bad choices out there just waiting for an opertunity). You seem to be a bright guy, I'll assume your ex isn't an idiot, too. When there's a punishment in one household, it should be so in the other. Even tho you couldn't make your marriage work out, for whatever reason, it really does take two parents to raise your offspring. Best advice I can give: care and be involved. Don't let discipline suffer. She totally has to hold up her end, also. Your kid's future is at stake.