I agree or consented in court to pay 35% out of my $1299. Monthly ssd benefit,now it $1150. Is court able to apply the 35% if I disagree in file petition for alesser amount

It depends on your state's CS guidelines.

Child support is normally based on income with often a min amount that is acceptable.

You can ask the court for a review, in some places it is done without formal hearing, by merely making a petition and submitting all of your income data

Have you looked into getting ssd benefits for each of your children since you are receiving disability?

Technically your ssd benefits should not be garnished for child support. You having agreed to this is costing you plenty every month. You need to look into getting the ssd benefits for each of your children and getting the court to stop the monthly garnishment of your ssd benefits. For the second item you may need an attorney's help to stop it.