I think there are quite a few people here that have more experience than me on the subject, so take this as you wish.
Basing this on my own experience (which had the potential of being really bad, but turned out actually to be quite "fair" obviously within the context of our society and current values, not saying I agree with those 100%, we won't go there), as well as what I saw from friends/work colleagues, in regards to kids when separating, the best strategy really is to concentrate on the well being of the kid(s), well because that's what's important, not your own pride or whatever else you might think, walking over your own pride for your kid, not only is not a sign of weakness, but actually shows true strength.
This will also:
- shows anybody involved in the situation that you have good intentions and you are a real dad that puts his kid before any separation/money bullshit
- having a different attitude won't diminish the amount $ you'll have to pay, actually a bad attitude might result in the opposite
- because your intentions become quite obvious, which is to take care of your kid, you can permit your self to ask some things, for example: I would like to spend a good part of the time that I have with my daughter to buy her clothes, as we always played dress up, would it be possible for me to buy most of her clothes, instead of giving the money to the mom, I'll obviously provide the bills
- if you've been a gentleman all along, not playing the blame game, or trying to argue on the pension amount for 10$.... than the above will most likely be accepted, even if the ex is more or less ok with it, it will be hard for her in front of everyone to oppose it... as you've been flawless remember, so she would be the one looking like the bad parent denying this dad that only cares about his daughter, this activity.
- No they won't be stupid, and they'll have a doubt about you doing this to make sure the money goes to your daughter and not trusting the mom with the money, but without really saying and without them really being sure of it and be able to judge you on it, considering again how flawless you've been.
You have to really rise above it, and be the better parent, the rest, with time, being the relation with your ex and her family, the amount of money you have to give to your ex and how she uses it, will end up falling into place, that's if you're not able to actually have it from the start.
Tell yourself this as much as woman can be vendictived bitches, with no heart, they still love their children and right now society teaches us that's very important for both parents to be part of the kids life and have a good relation with it, as if not the kid will suffer and indirectly so will she, even if she cares less about the kid, a troubled one will end up creating more "problems" for her, so in the end you should be able to come up with a certain agreement.
Obviously if you've slept like with her sister or mom, than not sure what to tell you, move to another province and start building another family there, cause you're fucked with this one.