Resist the urge to try to punish STBX through the D, it won't work. Resist the urge to try to make her pay emotionally or financially for her sins. It won't work. A D is simply a BUSINESS arrangement. It does not right and of the wrongs, it is no reflection of who is right or wrong, especially in your state. It is a BUSINESS arrangement.
Also, try to feel like less of a victim and take a more objective look at things. The support money is largely child support, yes? What percentage is child support and what percentage is spousal support? Doesn't spousal support drop off at some point? Just try to keep in mind that it is not simply pocket money for STBXW. The net worth of the family to be divided is what you accrued TOGETHER as a family. You are not simply handing over half of what was solely yours.
I know it feels differently right now, but that's how it is. An L I saw once said that a D settlement isn't fair until both people feel screwed. It's very true.
Now, what to do about the $720/year. I thought that was the number between you and finalizing an agreement. If so, then it really is probably worth just agreeing and getting this done. Delaying things will quickly eat up that much money in legal fees for years to come, STBX will come up with more demands, etc... Just FINISH it.
However, if you are in the MIDDLE of negotiations, that's a different matter. And, I think maybe you need to take a fresh look at things. If you are worried about buying a pair of jeans, you are not rolling in dough. The economy is poor. Your earning potential may stagnate or drop.
This D radically changes your standard of living. Face that and accept it. DD's life will be different now. Trying to make private school a legal requirement is perhaps not well-advised. Don't base this on what is going on at the moment, where you live, what job you have, what school STBX might pick. All those things are variable. In the long run, it seems better to not have private tuition be a state dictate. Also, if STBX is willing to contribute to tuition, she will probably do it without being ordered to do so by the court. If she isn't, she'll probably find herself unable to contribute to tuition even if the court orders her to do so.
So, this is my advice, and here I agree with NM -- it is far better that you have the freedom to spend the income over what would be ordered by the court as you choose to benefit DD, using it for summer camp, private tuition, etc...
(1) Guarantee yourself the best financial arrangement possible. This is a business arrangement. Don't try to control STBX's parenting choices or punish her with it. Just make the best financial deal possible. My guess is this means that you STOP negotiations. CA law is pretty clear, yes? I don't think the court will approve you paying less in child/spousal support than is required by law. But as long as the court is not going to make you pay more than is legally required, then just go with the court-mandated division, WITHOUT private school.
(2) If negotiations over physical property aren't very easy, again, let the court dictate the division. For the most part, you'll find yourself wanting entirely new stuff anyway.
So, basically, quit messing around with this and accept the court-ordered minimums and make zero legal commitments beyond that. This way you retain financial control over any funds you might be willing to contribute to support DD.
And, how you want to spend such funds will change over time. Your priorities will shift. It is, for instance, probably more important that you be financially secure when you retire than that DD go to private school. You will likely remarry. You'll probably find it more important to have another child than to pay for ski trips for DD. There will be changing financial priorities that affect what your choices today would be. This would be the same whether or not you remained married, BTW. But, no doubt, the impact of the shifting priorities will be more greatly felt because there will be less moolah.
As for STBX's ongoing financial requests:
(1) Settle any bill that affects your credit, being sure to deduct the amount from your net worth. Be proactive about this.
(2) Deny optional requests for other money until you have a legal financial settlement in place. "I am not willing to pay for that now, but keep a list of your requests and the court can consider them at the time of settlement."
Oh, and here is something to check with your L about. It might not be a good idea to limit your spending so much right now. When I got D, XH and I both had 10-15K in outstanding individual debt. In court, these amounts offset each other. ALL that mattered was the amount of debt. Of course, my debt was all old JOINTLY accrued debt. XH's debt was all spending after separation for stuff for his GF (like a car...) Too bad, so sad, offsetting individual debt. I can see the same thing happening with you and STBX, so again, check with your L.
