Can I have the case reopened?

You need to consult an attorney asap. You cannot let him have unsupervised parenting time with the child based on the events you described. ...

What is a conference, how does this girl go about getting this order of filtration, and child support order ?

He can agree wou the results or ask for a trial on the matter. He will likely lose the trial but he is he riht to a trial.

Can I modify child support payment if ex-spouse is financially irresponsible?

You need to make a change in custody and child support.

Do I have to pay retroactive child support when I supported the child 100 ?

You need to speak to an attorney asap. If an appeal is necessary than time is limited.

Is this correct yes or no

It is essentially true. If the child is not in a state in the U.S. For 6 months while under 18 then a petition cannot be filed in the U.S.

Does my ex have a custodial interference case against me because I took them back home earlier than planned?

One instance like you have described does not constitute custodial interference, but to say she put hem in harms way is a bit of an exaggeration....

Can my ex change custody arrangements that are currently working just because she feels like changing them?

If there is an order detailing visitation she cannot unilaterally change it.

What are the options here? Can he go about getting a law guardian on his own? If so, how?

If the children are in danger then the authorities should be called. Waiting for a court date when a judge would appoint a law guardian is not the...

Is there any way I can get his arrested or get a restraining order on him?

Talk to your parents and family. Explain that you have come to the point where it is not just kids fighting your brother is an adult who is...

The judge will weigh all the factors and based on the child's best interest decide if there should be supervised visits once you request them.