Can my husband be deported back to spain for a crime if he is married with children in the united states?

Yes. Depending on what his crime was, he may never be allowed to return. Marriage and children will not stop his deportation.

Of course! If he is a naturalized US citizen, there are a few crimes which can result in revocation of naturalized citizenship and deportation. E.g. if there is any fraud, perjury, forgery, etc, in any immigration-related application, interview, supporting documentation; war crimes; etc. If his status is anything other than naturalized citizen, many types of felonies will result in deportation, and some are mandatory deports. "Crimes of moral turpitude" such as drug-related offenses, violence, crimes against children, etc, are automatic bar to citizenship, and usually are crimes where deportation is mandatory.

His children have a right to citizenship in his country of citizenship. He should ensure his children have passports from his country of citizenship. If he's deported, they can go to his country at any time for any length of time without any immigration or visa hassles.

Yes depending on the crime committed. Most likely you and the children would have to follow him.

If Spain has an extradition treaty with the U.S. yes, your husband can be deported. Children are irrelevant.

Possibly, it depends on the severity of the crime.

Yes of course.

Yes, absolutely.

Far more info required

If he has a green card yes, citizen no!