I'm not 法居士

Sorry to hear you're getting divoce, especially you have children. Instead of going to court, why not sit down to talk to each other. As I know if you guys cannot make an agreement, a judge can ask you pay up to 20% for child support and an attorney could cost you thousands of $. You can get standard form from court for free. The amount for child support is negotiable but I don't think living in China is an execuse to pay less. The most important I think is legal custody instead of money. Thinking the happiness of raising a child, do you really want to lose him/her.

I don't think it will affect your GC application.

I'm not a lawyer, just some personal advices.

Good Luck.