Bless your co-parent just as they are. Let go of your expectations about co-parenting. Then parent as best you can. Release everyone, even yourself, from the expectations and dreams you had of a wonderful co-parenting relationship.
Two people agree to have kids and a huge shift happens in their lives and their future together. You are committing to a lifetime of connection with this person, even as you are agreeing to bring new dependants onto the planet. It's a massive transition, this becoming a parent. Deciding to divorce your co-parent is another huge shift.
When we started down the road of negotiating a cooperative divorce (because it's all about the children) our divorce and parenting plan counselor also suggested 70-30.
At some point along the way, I fell behind on my child support payments. I tried to be clear and honest about the situation. I asked for a bit of leeway in how I would repay her. And for whatever reason (I don't think it's healthy or helpful to say what another person is thinking) she felt it was in the best interest of the kids to file our decree with the Attorney General's office.