If I file for temporary custody or guardianship of my son will CPS take him?

I concur with my colleague. CPS would not get involved unless someone calls them.

Perhaps that may mean termination of status. Hard to say without case number and minute order.

Service must be done by anyone over the age of 18 and not you.

My adult son (22) birth certificate doesn't have his dad's name on it. What is the process to put the name on the birth certi??

I concur with my colleague. Google is great and free for doing name changes.

Where do I start to gain back custody of my daughter from my mother?

Parenting classes and rehabilitation are a key starting point. Long and tough road, but that will get you headed in the right direction.

Can I file a declaration of default for an Ex Parte?

I believe you are talking about a Request for Orders. Yes, if he does not file a response, you can request the court take his default.

Can I hold my childs visitation with his Mother ?

That won't past muster. Time to move on is what the court would say (absent a second offender or drug addict).

Absolutely not. Bad idea. If you have children together, only the parents should communicate and co-parent.

How hard is it to get 50/50 physical custody of my child?

I concur with my colleague. Hire an experienced family law attorney.

My son got hurt by a stud on a standpipe.

Great civil litigation question. Best of luck.