1. How accurate does it have to be?
my L was recommended to me as ethical, and she was ethical. she said list everything you can think of and label it correctly, so that you'll be safe if challenged. this doesn't mean to-the-dollar, but it does mean an honest estimate. if it begins to appear that you're inflating your spending claims or hiding money you'd be open to accusations of fraud and that's the worst thing you can face. same goes for the other party of course, so when you see his statement go over it carefully.
2. Should I write right now situation or factor in definite future spending such as insurance after divorce or kids' activities? or do I leave them as $0?
ask your L.
3. What is this form for?
we didn't have children so in my case it was the basis on which negotiations over division of assets would begin.
4. What if I spend $250 for dinning out and he spends for $500?
unfortunately (if you're like me and you live modestly but your spouse treats money like water) the courts give wide latitude to "lifestyle choices". this was one of the angering things going into my negotiations: that because of my responsibility i was going to lose more money than if i had spent more freely.
5. Nowhere to put lawyers fee.
there should be.
for comparison, here is the NYS Statement of Net Worth:
https://www.nycourts.gov/forms/matrimonial/networth.pdf. on p. 13 there a line for counsel fees.