Your husband's lawyer is in the best position to assert his rights. If you're not happy with the job they're doing, you have the option to hire private counsel; someone who will have more time to devote to this case.
Remember that the District Attorney is the prosecutor!!
Anything you say to the District Attorney can turn around and be used against any of the defendants, possibly even your husband. It can also make you a "witness" and subject to be called to testify at trial.
Speak to your husband's attorney. He or she should know how the information can assist your husband and how to use it, for the best benefit to your husband.
NO, NO and NO. The DA won't talk to you anyway. A defense attorneys job is protect the interest of their client. That why each defendant has a separate attorney - to look after their individual interests. A defense attorney can't help a co-Defendant - that's not his job and would get him disbarred. Your husband's attorney is the one to fight for him. Let him do his job because if you get involved, you'll only make things worse.