i'm concerned with the keeping secrets part - that part of your plan depends upon others who are close/related to your husband keeping their mouths shut about you calling etc.
he IS sober now? still? this might be the best time to tell him you DID call his parents out of an abundance of concern. that you were at wit's end, concerned for him, concerned for yourself.
i'd much rather be out in front of such a thing rather than get blindslided by it later. besides your "secret" relies on way too many people and really, shouldn't even BE a secret.
if you are THAT scared of telling him the truth then really what ARE you sticking around for?