oh, dear, that sounds complex and gruelling for all of you!
As you're using a lot of technical legal vocabulary I don't know, I can't begin to answer your questions about the legal side of things. Perhaps this organisation, specifically for couples across two countries, might be able to advise you: http://www.binational.ch/en/?Counseling_offices
And here, only in German, are suggested standard Swiss budgets for a single parent with 1, 2 or 3 children: http://www.budgetberatung.ch/Budget-...ende.96.0.html
If the items are not clear to you, most probably you could use "Google translate" to understand the forms.
You might compare those budget figures (and vocabluary) with the suggestions of the Swiss French-language consumer organisation: http://www.frc.ch/utile-au-quotidien...iches-conseil/
(scroll down to see "Personne seule avec enfant(s)" (= single person with children).