What has to be the most frustrating thing is how the WAS seems to go about the destruction of an M and family, as though they are breaking up some highschool, summer romance...
While we DB for ourselves and most who come here at least initially want to stand for our Ms, you are in a fairly poor position to just sit and wait...
Now what the agent told you may or may not be true (not saying it's wrong, just be careful what you believe, regardless of whether the source is reliable)... until your H actually files, then he hasn't filed and it's not worth worrying about...
BUT... in your case, I'd have to say my opinion is consult an L as soon as possible to protect you and your kids! Let's just say that your H DOES file once you're off mat leave... until you talk to a L, you will have no real idea what the implications might be...
And as always, understand that if you start proceedings, you can always put them on the back burner...