How can I know if there is any bench warrant issued against me for child support?

Yes, you can (or hire an attorney in NY) call the court where the matter was pending and find out about the status of the matter. Do so...

Can i go visit him ? Being that we had an order of protection before or is it okay for me to visit him since the OP expired?

If the OP is EXPIRED, there is nothing preventing you from visiting him at the jail if that is the only issue.

It can take up to 2 weeks sometimes. Be patient and in the meantime, do NOT drive.

What will the cops do with that information? Was it legal for them to go through the back gates?

If they had probable cause that a crime was being committed at that time, the had the right to enter onto your property. Luckily for you and your...

Is accepting the misdemeanor my only choice?

This is a discussion that needs to be had with your lawyer. Do you have a private attorney? If not, i would suggest hiring one.

If your arrested in NY, and your case later gets dismissed and sealed, does the ARREST record show? Like being handcuffed?

If the complete matter was dismissed and sealed, it should NOT show up on a subsequent background check with a few exceptions (law enforcement).

Whats gonna happen to my buddy?

It's a serious charge and your friend should retain an experienced attorney immediately

Can I lose my nursing license if I let my son, a convicted non violent felon live with me?

No, there are no restrictions in regard to who you live with

My lawyer wants to me about my plea deal then she said we should talk about downward departure what does that mean do i file it.

You do not do anything. Your attorney does it. Your attorney will try to limit your time you are facing in custody of you take a plea

What can we do to keep him out of jail?

Your son was lucky that NYC decided not to extradite him. But, if he wants to take care of the matter now and not have to live with this warrant...