I think your best answer is that you need to engage a skilled criminal defense lawyer to assist YOU!
The technical issues of who has the privledge and how it applies are beyond me. But as I understand it the spouse has broad rights to prevent you from testifying against him. But you can testify for him. Problem is you are not supposed to lie--and if you tell two different stories that sort of says one is wrong and you are stepping into lying on the stand--which could get you jail time ! And at teh very least it totally discredits you--which may be waht PD has in mind.
But that s not the question you pose---apparently you pose that the PD has "suggested" that you lie and reinvent the story? My guess is PD is sure to deny same and you will be left to swing in the wind. On the otherhand if you cooperate with prosecution you may be aiding the outcome you don't want.
I frankly think its such a Catch 22 that you almost certainly gotta have your own skilled criminal defesne counsel to assist you