My husband left us and moved out of state. He says that he is going to find a job and get us a place and when he does we will all be moving out with him. He has also made threats that he is going to take our son. I want us all to be together and if he knows I am trying to get temporary custody he will think I have other intentions other than protecting our son for the time being.

You will have to serve him with papers that there will be a hearing. He has the right to be at the hearing and file objections to it

Yes the court will require that he be notified. Why do you think you need to file for temp custody?

My husband has been getting frustrated that his plan to get a job is not working and he has been making threats about just coming back and taking our son which is why I think I need temporary custody till we decide if we will be getting a divorce or not.

So file for a legal separation with temp custody. But he will need to be informed.